express-zod-api
Advanced tools
A Typescript library to help you get an API server up and running with I/O schema validation and custom middlewares in minutes.
Start your API server with I/O schema validation and custom middlewares in minutes.
You can find the release notes and migration guides in Changelog.
I made this library because of the often repetitive tasks of starting a web server APIs with the need to validate input data. It integrates and provides the capabilities of popular web server, logging, validation and documenting solutions. Therefore, many basic tasks can be accomplished faster and easier, in particular:
These people contributed to the improvement of the library by reporting bugs, making changes and suggesting ideas:
The API operates object schemas for input and output validation.
The object being validated is the combination of certain request properties.
It is available to the endpoint handler as the input parameter.
Middlewares have access to all request properties, they can provide endpoints with options.
The object returned by the endpoint handler is called output. It goes to the ResultHandler which is
responsible for transmitting consistent responses containing the output or possible error.
Much can be customized to fit your needs.
info(), debug(), error() and warn() methods;
Install the library, its peer dependencies and type assistance packages using your favorite package manager.
# example for yarn and express 5 (recommended):
yarn add express-zod-api express@^5 zod typescript http-errors
yarn add -D @types/express@^5 @types/node @types/http-errors
Ensure having the following options in your tsconfig.json file in order to make it work as expected:
{
"compilerOptions": {
"strict": true,
"skipLibCheck": true
}
}
Create a minimal configuration. See all available options in sources.
import { createConfig } from "express-zod-api";
const config = createConfig({
server: {
listen: 8090, // port, UNIX socket or options
},
cors: true,
logger: { level: "debug", color: true },
});
In the basic case, you can just import and use the default factory. See also Middlewares and Response customization.
import { defaultEndpointsFactory } from "express-zod-api";
The endpoint responds with "Hello, World" or "Hello, {name}" if the name is supplied within GET request payload.
import { z } from "zod";
const helloWorldEndpoint = defaultEndpointsFactory.build({
method: "get", // or methods: ["get", "post", ...]
input: z.object({
// for empty input use z.object({})
name: z.string().optional(),
}),
output: z.object({
greetings: z.string(),
}),
handler: async ({ input: { name }, options, logger }) => {
logger.debug("Options:", options); // middlewares provide options
return { greetings: `Hello, ${name || "World"}. Happy coding!` };
},
});
Connect your endpoint to the /v1/hello route:
import { Routing } from "express-zod-api";
const routing: Routing = {
v1: {
hello: helloWorldEndpoint,
},
};
See the complete implementation example.
import { createServer } from "express-zod-api";
createServer(config, routing);
Start your application and execute the following command:
curl -L -X GET 'localhost:8090/v1/hello?name=Rick'
You should receive the following response:
{ "status": "success", "data": { "greetings": "Hello, Rick. Happy coding!" } }
Middleware can authenticate using input or request headers, and can provide endpoint handlers with options.
Inputs of middlewares are also available to endpoint handlers within input.
Here is an example of the authentication middleware, that checks a key from input and token from headers:
import { z } from "zod";
import createHttpError from "http-errors";
import { Middleware } from "express-zod-api";
const authMiddleware = new Middleware({
security: {
// this information is optional and used for generating documentation
and: [
{ type: "input", name: "key" },
{ type: "header", name: "token" },
],
},
input: z.object({
key: z.string().min(1),
}),
handler: async ({ input: { key }, request, logger }) => {
logger.debug("Checking the key and token");
const user = await db.Users.findOne({ key });
if (!user) {
throw createHttpError(401, "Invalid key");
}
if (request.headers.token !== user.token) {
throw createHttpError(401, "Invalid token");
}
return { user }; // provides endpoints with options.user
},
});
By using .addMiddleware() method before .build() you can connect it to the endpoint:
const yourEndpoint = defaultEndpointsFactory
.addMiddleware(authMiddleware)
.build({
// ...,
handler: async ({ options }) => {
// options.user is the user returned by authMiddleware
},
});
You can create a new factory by connecting as many middlewares as you want — they will be executed in the specified
order for all the endpoints produced on that factory. You may also use a shorter inline syntax within the
.addMiddleware() method, and have access to the output of the previously executed middlewares in chain as options:
import { defaultEndpointsFactory } from "express-zod-api";
const factory = defaultEndpointsFactory
.addMiddleware(authMiddleware) // add Middleware instance or use shorter syntax:
.addMiddleware({
input: z.object({}),
handler: async ({ options: { user } }) => ({}), // options.user from authMiddleware
});
In case you'd like to provide your endpoints with options that do not depend on Request, like non-persistent connection
to a database, consider shorthand method addOptions. For static options consider reusing const across your files.
import { readFile } from "node:fs/promises";
import { defaultEndpointsFactory } from "express-zod-api";
const endpointsFactory = defaultEndpointsFactory.addOptions(async () => {
// caution: new connection on every request:
const db = mongoose.connect("mongodb://connection.string");
const privateKey = await readFile("private-key.pem", "utf-8");
return { db, privateKey };
});
Notice on resources cleanup: If necessary, you can release resources at the end of the request processing in a custom Result Handler:
import { ResultHandler } from "express-zod-api";
const resultHandlerWithCleanup = new ResultHandler({
handler: ({ options }) => {
// necessary to check for certain option presence:
if ("db" in options && options.db) {
options.db.connection.close(); // sample cleanup
}
},
});
There are two ways of connecting the native express middlewares depending on their nature and your objective.
In case it's a middleware establishing and serving its own routes, or somehow globally modifying the behaviour, or
being an additional request parser (like cookie-parser), use the beforeRouting option.
However, it might be better to avoid cors here — the library handles it on its own.
import { createConfig } from "express-zod-api";
import ui from "swagger-ui-express";
const config = createConfig({
server: {
listen: 80,
beforeRouting: ({ app, logger, getChildLogger }) => {
logger.info("Serving the API documentation at https://example.com/docs");
app.use("/docs", ui.serve, ui.setup(documentation));
},
},
});
In case you need a special processing of request, or to modify the response for selected endpoints, use the method
addExpressMiddleware() of EndpointsFactory (or its alias use()). The method has two optional features: a provider
of options and an error transformer for adjusting the response status code.
import { defaultEndpointsFactory } from "express-zod-api";
import createHttpError from "http-errors";
import { auth } from "express-oauth2-jwt-bearer";
const factory = defaultEndpointsFactory.use(auth(), {
provider: (req) => ({ auth: req.auth }), // optional, can be async
transformer: (err) => createHttpError(401, err.message), // optional
});
You can implement additional validations within schemas using refinements.
Validation errors are reported in a response with a status code 400.
import { z } from "zod";
import { Middleware } from "express-zod-api";
const nicknameConstraintMiddleware = new Middleware({
input: z.object({
nickname: z
.string()
.min(1)
.refine(
(nick) => !/^\d.*$/.test(nick),
"Nickname cannot start with a digit",
),
}),
// ...,
});
By the way, you can also refine the whole I/O object, for example in case you need a complex validation of its props.
const endpoint = endpointsFactory.build({
input: z
.object({
email: z.string().email().optional(),
id: z.string().optional(),
otherThing: z.string().optional(),
})
.refine(
(inputs) => Object.keys(inputs).length >= 1,
"Please provide at least one property",
),
// ...,
});
Since parameters of GET requests come in the form of strings, there is often a need to transform them into numbers or arrays of numbers.
import { z } from "zod";
const getUserEndpoint = endpointsFactory.build({
method: "get",
input: z.object({
id: z.string().transform((id) => parseInt(id, 10)),
ids: z
.string()
.transform((ids) => ids.split(",").map((id) => parseInt(id, 10))),
}),
handler: async ({ input: { id, ids }, logger }) => {
logger.debug("id", id); // type: number
logger.debug("ids", ids); // type: number[]
},
});
For some APIs it may be important that public interfaces such as query parameters use snake case, while the
implementation itself requires camel case for internal naming. In order to facilitate interoperability between the
different naming standards you can .transform() the entire input schema into another object using a well-typed
mapping library, such as camelize-ts. However, that approach would not be
enough for the output schema if you're also aiming to generate a valid documentation,
because the transformations themselves do not contain schemas. Addressing this case, the library offers the .remap()
method of the object schema, a part of the Zod plugin, which under the hood, in addition to the
transformation, also .pipe() the transformed object into a new object schema.
Here is a recommended solution: it is important to use shallow transformations only.
import camelize from "camelize-ts";
import snakify from "snakify-ts";
import { z } from "zod";
const endpoint = endpointsFactory.build({
method: "get",
input: z
.object({ user_id: z.string() })
.transform((inputs) => camelize(inputs, /* shallow: */ true)),
output: z
.object({ userName: z.string() })
.remap((outputs) => snakify(outputs, /* shallow: */ true)),
handler: async ({ input: { userId }, logger }) => {
logger.debug("user_id became userId", userId);
return { userName: "Agneta" }; // becomes "user_name" in response
},
});
The .remap() method can also accept an object with an explicitly defined naming of your choice. The original keys
missing in that object remain unchanged (partial mapping).
z.object({ user_name: z.string(), id: z.number() }).remap({
user_name: "weHAVEreallyWEIRDnamingSTANDARDS", // "id" remains intact
});
Dates in Javascript are one of the most troublesome entities. In addition, Date cannot be passed directly in JSON
format. Therefore, attempting to return Date from the endpoint handler results in it being converted to an ISO string
in actual response by calling
toJSON(),
which in turn calls
toISOString().
It is also impossible to transmit the Date in its original form to your endpoints within JSON. Therefore, there is
confusion with original method z.date() that should not be used within IO schemas of your API.
In order to solve this problem, the library provides two custom methods for dealing with dates: ez.dateIn() and
ez.dateOut() for using within input and output schemas accordingly.
ez.dateIn() is a transforming schema that accepts an ISO string representation of a Date, validates it, and
provides your endpoint handler or middleware with a Date. It supports the following formats:
2021-12-31T23:59:59.000Z
2021-12-31T23:59:59Z
2021-12-31T23:59:59
2021-12-31
ez.dateOut(), on the contrary, accepts a Date and provides ResultHanlder with a string representation in ISO
format for the response transmission. Consider the following simplified example for better understanding:
import { z } from "zod";
import { ez, defaultEndpointsFactory } from "express-zod-api";
const updateUserEndpoint = defaultEndpointsFactory.build({
method: "post",
input: z.object({
userId: z.string(),
birthday: ez.dateIn(), // string -> Date
}),
output: z.object({
createdAt: ez.dateOut(), // Date -> string
}),
handler: async ({ input }) => {
// input.birthday is Date
return {
// transmitted as "2022-01-22T00:00:00.000Z"
createdAt: new Date("2022-01-22"),
};
},
});
You can enable your API for other domains using the corresponding configuration option cors.
It's not optional to draw your attention to making the appropriate decision, however, it's enabled in the
Quick start example above, assuming that in most cases you will want to enable this feature.
See MDN article for more information.
In addition to being a boolean, cors can also be assigned a function that overrides default CORS headers.
That function has several parameters and can be asynchronous.
import { createConfig } from "express-zod-api";
const config = createConfig({
// ... other options
cors: ({ defaultHeaders, request, endpoint, logger }) => ({
...defaultHeaders,
"Access-Control-Max-Age": "5000",
}),
});
Please note: If you only want to send specific headers on requests to a specific endpoint, consider the Middlewares or response customization approach.
The modern API standard often assumes the use of a secure data transfer protocol, confirmed by a TLS certificate, also
often called an SSL certificate in habit. When using the createServer() method, you can additionally configure and
run the HTTPS server.
import { createConfig, createServer } from "express-zod-api";
const config = createConfig({
server: {
listen: 80,
},
https: {
options: {
cert: fs.readFileSync("fullchain.pem", "utf-8"),
key: fs.readFileSync("privkey.pem", "utf-8"),
},
listen: 443, // port, UNIX socket or options
},
// ... cors, logger, etc
});
// 'await' is only needed if you're going to use the returned entities.
// For top level CJS you can wrap you code with (async () => { ... })()
const { app, httpServer, httpsServer, logger } = await createServer(
config,
routing,
);
Ensure having @types/node package installed. At least you need to specify the port (usually it is 443) or UNIX socket,
certificate and the key, issued by the certifying authority. For example, you can acquire a free TLS certificate for
your API at Let's Encrypt.
If the simple console output of the built-in logger is not enough for you, you can connect any other compatible one.
It must support at least the following methods: info(), debug(), error() and warn().
Winston and Pino support is well known. Here is an example configuring pino logger with pino-pretty extension:
import pino, { Logger } from "pino";
import { createConfig } from "express-zod-api";
const logger = pino({
transport: {
target: "pino-pretty",
options: { colorize: true },
},
});
const config = createConfig({ logger });
// Setting the type of logger used
declare module "express-zod-api" {
interface LoggerOverrides extends Logger {}
}
In case you need a dedicated logger for each request (for example, equipped with a request ID), you can specify the
childLoggerProvider option in your configuration. The function accepts the initially defined logger and the request,
it can also be asynchronous. The child logger returned by that function will replace the logger in all handlers.
You can use the .child() method of the built-in logger or install a custom logger instead.
import { createConfig, BuiltinLogger } from "express-zod-api";
import { randomUUID } from "node:crypto";
// This enables the .child() method on "logger":
declare module "express-zod-api" {
interface LoggerOverrides extends BuiltinLogger {}
}
const config = createConfig({
logger: { level: "debug", color: true },
childLoggerProvider: ({ parent, request }) =>
parent.child({ requestId: randomUUID() }),
});
For debugging and performance testing purposes the library offers a simple .profile() method on the built-in logger.
It starts a timer when you call it and measures the duration in adaptive units (from picoseconds to minutes) until you
invoke the returned callback. The default severity of those measurements is debug.
import { createConfig, BuiltinLogger } from "express-zod-api";
// This enables the .profile() method on "logger":
declare module "express-zod-api" {
interface LoggerOverrides extends BuiltinLogger {}
}
const config = createConfig({ logger: { level: "debug", color: true } });
// Inside a handler of Endpoint, Middleware or ResultHandler:
const done = logger.profile("expensive operation");
doExpensiveOperation();
done(); // debug: expensive operation '555 milliseconds'
You can also customize the profiler with your own formatter, chosen severity or even performance assessment function:
logger.profile({
message: "expensive operation",
severity: (ms) => (ms > 500 ? "error" : "info"), // assess immediately
formatter: (ms) => `${ms.toFixed(2)}ms`, // custom format
});
doExpensiveOperation();
done(); // error: expensive operation '555.55ms'
According to Express.js best practices guide it might be a good idea to enable GZIP compression of your API responses.
Install the following additional packages: compression and @types/compression, and enable or configure compression:
import { createConfig } from "express-zod-api";
const config = createConfig({
server: {
/** @link https://www.npmjs.com/package/compression#options */
compression: { threshold: "1kb" }, // or true
},
});
In order to receive a compressed response the client should include the following header in the request:
Accept-Encoding: gzip, deflate. Only responses with compressible content types are subject to compression.
You can customize the list of request properties that are combined into input that is being validated and available
to your endpoints and middlewares. The order here matters: each next item in the array has a higher priority than its
previous sibling.
import { createConfig } from "express-zod-api";
createConfig({
inputSources: {
// the defaults are:
get: ["query", "params"],
post: ["body", "params", "files"],
put: ["body", "params"],
patch: ["body", "params"],
delete: ["query", "params"],
}, // ...
});
You can describe the route of the endpoint using parameters:
import { Routing } from "express-zod-api";
const routing: Routing = {
v1: {
user: {
// route path /v1/user/:id, where :id is the path param
":id": getUserEndpoint,
// use the empty string to represent /v1/user if needed:
// "": listAllUsersEndpoint,
},
},
};
You then need to specify these parameters in the endpoint input schema in the usual way:
const getUserEndpoint = endpointsFactory.build({
method: "get",
input: z.object({
// id is the route path param, always string
id: z.string().transform((value) => parseInt(value, 10)),
// other inputs (in query):
withExtendedInformation: z.boolean().optional(),
}),
output: z.object({
/* ... */
}),
handler: async ({ input: { id } }) => {
// id is the route path param, number
},
});
Thanks to the DependsOnMethod class a route may have multiple Endpoints attached depending on different methods.
It can also be the same Endpoint that handles multiple methods as well.
import { DependsOnMethod } from "express-zod-api";
// the route /v1/user has two Endpoints
// which handle a couple of methods each
const routing: Routing = {
v1: {
user: new DependsOnMethod({
get: yourEndpointA,
delete: yourEndpointA,
post: yourEndpointB,
patch: yourEndpointB,
}),
},
};
See also Different responses for different status codes.
ResultHandler is responsible for transmitting consistent responses containing the endpoint output or an error.
The defaultResultHandler sets the HTTP status code and ensures the following type of the response:
type DefaultResponse<OUT> =
| {
// Positive response
status: "success";
data: OUT;
}
| {
// or Negative response
status: "error";
error: {
message: string;
};
};
You can create your own result handler by using this example as a template:
import { z } from "zod";
import {
ResultHandler,
getStatusCodeFromError,
getMessageFromError,
} from "express-zod-api";
const yourResultHandler = new ResultHandler({
positive: (data) => ({
schema: z.object({ data }),
mimeType: "application/json", // optinal, or mimeTypes for array
}),
negative: z.object({ error: z.string() }),
handler: ({ error, input, output, request, response, logger }) => {
if (!error) {
// your implementation
return;
}
const statusCode = getStatusCodeFromError(error);
const message = getMessageFromError(error);
// your implementation
},
});
See also Different responses for different status codes.
After creating your custom ResultHandler you can use it as an argument for EndpointsFactory instance creation:
import { EndpointsFactory } from "express-zod-api";
const endpointsFactory = new EndpointsFactory(yourResultHandler);
ResultHandler is designed to be the entity responsible for centralized error handling. By default, that center is
the defaultResultHandler, however, since much can be customized, you should be aware that there are three possible
origins of errors that could happen in runtime and be handled the following way:
Endpoint execution — handled by a ResultHandler assigned to the EndpointsFactory produced it:
InputValidationError — when request payload does not match the input schema of the endpoint.
The default response status code is 400;OutputValidationError — when returns of the endpoint's handler does not match its output schema (500);handler:
HttpError, made by createHttpError() method of http-errors (required peer dependency). The default response
status code is taken from error.statusCode;Error class (500);ResultHandler assigned to errorHandler in config:
defaultResultHandler — it sets the response status code from the corresponding HttpError:
400 for parsing, 404 for routing, config.upload.limitError.statusCode for upload issues, or 500 for others.ResultHandler must handle possible error and avoid throwing its own errors, otherwise:ResultHandler execution — handled by LastResortHandler:
500 and the response itself is a plain text containing original error.message.Thus, you can configure non-object responses too, for example, to send an image file.
You can find two approaches to EndpointsFactory and ResultHandler implementation
in this example.
One of them implements file streaming, in this case the endpoint just has to provide the filename.
The response schema generally may be just z.string(), but I made more specific ez.file() that also supports
ez.file("binary") and ez.file("base64") variants which are reflected in the
generated documentation.
const fileStreamingEndpointsFactory = new EndpointsFactory(
new ResultHandler({
positive: { schema: ez.file("buffer"), mimeType: "image/*" },
negative: { schema: z.string(), mimeType: "text/plain" },
handler: ({ response, error, output }) => {
if (error) {
response.status(400).send(error.message);
return;
}
if ("filename" in output) {
fs.createReadStream(output.filename).pipe(
response.type(output.filename),
);
} else {
response.status(400).send("Filename is missing");
}
},
}),
);
Install the following additional packages: express-fileupload and @types/express-fileupload, and enable or
configure file uploads:
import { createConfig } from "express-zod-api";
const config = createConfig({
server: {
upload: true, // or options
},
});
Refer to documentation on available options.
Some options are forced in order to ensure the correct workflow: abortOnLimit: false, parseNested: true, logger
is assigned with .debug() method of the configured logger, and debug is enabled by default.
The limitHandler option is replaced by the limitError one. You can also connect an additional middleware for
restricting the ability to upload using the beforeUpload option. So the configuration for the limited and restricted
upload might look this way:
import createHttpError from "http-errors";
const config = createConfig({
server: {
upload: {
limits: { fileSize: 51200 }, // 50 KB
limitError: createHttpError(413, "The file is too large"), // handled by errorHandler in config
beforeUpload: ({ request, logger }) => {
if (!canUpload(request)) {
throw createHttpError(403, "Not authorized");
}
},
},
},
});
Then you can change the Endpoint to handle requests having the multipart/form-data content type instead of JSON by
using ez.upload() schema. Together with a corresponding configuration option, this makes it possible to handle file
uploads. Here is a simplified example:
import { z } from "zod";
import { ez, defaultEndpointsFactory } from "express-zod-api";
const fileUploadEndpoint = defaultEndpointsFactory.build({
method: "post",
input: z.object({
avatar: ez.upload(), // <--
}),
output: z.object({}),
handler: async ({ input: { avatar } }) => {
// avatar: {name, mv(), mimetype, data, size, etc}
// avatar.truncated is true on failure when limitError option is not set
},
});
You can still send other data and specify additional input parameters, including arrays and objects.
In case you want your server to serve static files, you can use new ServeStatic() in Routing using the arguments
similar to express.static().
The documentation on these arguments you may find here.
import { Routing, ServeStatic } from "express-zod-api";
import { join } from "node:path";
const routing: Routing = {
// path /public serves static files from ./assets
public: new ServeStatic(join(__dirname, "assets"), {
dotfiles: "deny",
index: false,
redirect: false,
}),
};
If you already have your own configured express application, or you find the library settings not enough, you can
connect the endpoints to your app or any express router using the attachRouting() method:
import express from "express";
import { createConfig, attachRouting, Routing } from "express-zod-api";
const app = express(); // or express.Router()
const config = createConfig({ app /* cors, logger, ... */ });
const routing: Routing = {}; // your endpoints go here
const { notFoundHandler, logger } = attachRouting(config, routing);
app.use(notFoundHandler); // optional
app.listen();
logger.info("Glory to science!");
Please note that in this case you probably need to parse request.body, call app.listen() and handle 404
errors yourself. In this regard attachRouting() provides you with notFoundHandler which you can optionally connect
to your custom express app.
Besides that, if you're looking to include additional request parsers, or a middleware that establishes its own routes,
then consider using the beforeRouting option in config instead.
The way to test endpoints is to mock the request, response, and logger objects, invoke the execute() method, and
assert the expectations on status, headers and payload. The library provides a special method testEndpoint that
makes mocking easier. Under the hood, request and response object are mocked using the
node-mocks-http library, therefore you can utilize its API for
settings additional properties and asserting expectation using the provided getters, such as ._getStatusCode().
import { testEndpoint } from "express-zod-api";
test("should respond successfully", async () => {
const { responseMock, loggerMock } = await testEndpoint({
endpoint: yourEndpoint,
requestProps: {
method: "POST", // default: GET
body: {}, // incoming data as if after parsing (JSON)
}, // responseOptions, configProps, loggerProps
});
expect(loggerMock._getLogs().error).toHaveLength(0);
expect(responseMock._getStatusCode()).toBe(200);
expect(responseMock._getHeaders()).toHaveProperty("x-custom", "one"); // lower case!
expect(responseMock._getJSONData()).toEqual({ status: "success" });
});
Middlewares can also be tested individually, similar to endpoints, but using the
testMiddleware() method. There is also an ability to pass options collected from outputs of previous middlewares,
if the one being tested somehow depends on them.
import { z } from "zod";
import { Middleware, testMiddleware } from "express-zod-api";
const middleware = new Middleware({
input: z.object({ test: z.string() }),
handler: async ({ options, input: { test } }) => ({
collectedOptions: Object.keys(options),
testLength: test.length,
}),
});
const { output, responseMock, loggerMock } = await testMiddleware({
middleware,
requestProps: { method: "POST", body: { test: "something" } },
options: { prev: "accumulated" }, // responseOptions, configProps, loggerProps
});
expect(loggerMock._getLogs().error).toHaveLength(0);
expect(output).toEqual({ collectedOptions: ["prev"], testLength: 9 });
In some special cases you may want the ResultHandler to respond slightly differently depending on the status code,
for example if your API strictly follows REST standards. It may also be necessary to reflect this difference in the
generated Documentation. For that purpose, the constructor of ResultHandler accepts flexible declaration of possible
response schemas and their corresponding status codes.
import { ResultHandler } from "express-zod-api";
new ResultHandler({
positive: (data) => ({
statusCodes: [201, 202], // created or will be created
schema: z.object({ status: z.literal("created"), data }),
}),
negative: [
{
statusCode: 409, // conflict: entity already exists
schema: z.object({ status: z.literal("exists"), id: z.number().int() }),
},
{
statusCodes: [400, 500], // validation or internal error
schema: z.object({ status: z.literal("error"), reason: z.string() }),
},
],
handler: ({ error, response, output }) => {
// your implementation here
},
});
Please avoid doing this in new projects: responding with array is a bad practice keeping your endpoints from evolving
in backward compatible way (without making breaking changes). Nevertheless, for the purpose of easier migration of
legacy APIs to this library consider using arrayResultHandler or arrayEndpointsFactory instead of default ones,
or implement your own ones in a similar way.
The arrayResultHandler expects your endpoint to have items property in the output object schema. The array
assigned to that property is used as the response. This approach also supports examples, as well as documentation and
client generation. Check out the example endpoint for more details.
In a similar way you can enable the inclusion of request headers into the input sources. This is an opt-in feature. Please note:
x- prefix) will be combined into the input,import { createConfig, defaultEndpointsFactory } from "express-zod-api";
import { z } from "zod";
createConfig({
inputSources: {
get: ["query", "headers"],
}, // ...
});
defaultEndpointsFactory.build({
method: "get",
input: z.object({
"x-request-id": z.string(), // this one is from request.headers
id: z.string(), // this one is from request.query
}), // ...
});
Some APIs may require an endpoint to be able to accept and process raw data, such as streaming or uploading a binary
file as an entire body of request. Use the proprietary ez.raw() schema as the input schema of your endpoint.
The default parser in this case is express.raw(). You can customize it by assigning the rawParser option in config.
The raw data is placed into request.body.raw property, having type Buffer.
import { defaultEndpointsFactory, ez } from "express-zod-api";
const rawAcceptingEndpoint = defaultEndpointsFactory.build({
method: "post",
input: ez.raw({
/* the place for additional inputs, like route params, if needed */
}),
output: z.object({ length: z.number().int().nonnegative() }),
handler: async ({ input: { raw } }) => ({
length: raw.length, // raw is Buffer
}),
});
You can enable and configure a special request monitoring that, if it receives a signal to terminate a process, will first put the server into a mode that rejects new requests, attempt to complete started requests within the specified time, and then forcefully stop the server and terminate the process.
import { createConfig } from "express-zod-api";
createConfig({
gracefulShutdown: {
timeout: 1000,
events: ["SIGINT", "SIGTERM"],
},
});
If you want the user of a client application to be able to subscribe to subsequent updates initiated by the server, the
capabilities of this library and the HTTP protocol itself would not be enough in this case. I have developed an
additional pluggable library, Zod Sockets, which has similar principles and
capabilities, but uses the websocket transport and Socket.IO protocol for that purpose. Check out an example of the
synergy between two libraries on handling the incoming subscribe and unsubscribe events in order to emit
(broadcast) the time event every second with a current time in its payload:
https://github.com/RobinTail/zod-sockets#subscriptions
Express Zod API acts as a plugin for Zod, extending its functionality once you import anything from express-zod-api:
.example() method to all Zod schemas for storing examples and reflecting them in the generated documentation;.label() method to ZodDefault for replacing the default value in documentation with a label;.remap() method to ZodObject for renaming object properties in a suitable way for making documentation;.brand() method on all Zod schemas by making the assigned brand available in runtime.You can generate a Typescript file containing the IO types of your API and a client for it.
Consider installing prettier and using the async printFormatted() method.
import { Integration } from "express-zod-api";
const client = new Integration({
routing,
variant: "client", // <— optional, see also "types" for a DIY solution
optionalPropStyle: { withQuestionMark: true, withUndefined: true }, // optional
splitResponse: false, // optional, prints the positive and negative response types separately
});
const prettierFormattedTypescriptCode = await client.printFormatted(); // or just .print() for unformatted
Alternatively, you can supply your own format function into that method or use a regular print() method instead.
The generated client is flexibly configurable on the frontend side using an implementation function that
directly makes requests to an endpoint using the libraries and methods of your choice.
The client asserts the type of request parameters and response.
Consuming the generated client requires Typescript version 4.1 or higher.
// example frontend, simple implementation based on fetch()
import { ExpressZodAPIClient } from "./client.ts"; // the generated file
const client = new ExpressZodAPIClient(async (method, path, params) => {
const hasBody = !["get", "delete"].includes(method);
const searchParams = hasBody ? "" : `?${new URLSearchParams(params)}`;
const response = await fetch(`https://example.com${path}${searchParams}`, {
method: method.toUpperCase(),
headers: hasBody ? { "Content-Type": "application/json" } : undefined,
body: hasBody ? JSON.stringify(params) : undefined,
});
return response.json();
});
client.provide("get", "/v1/user/retrieve", { id: "10" });
client.provide("post", "/v1/user/:id", { id: "10" }); // it also substitues path params
You can generate the specification of your API and write it to a .yaml file, that can be used as the documentation:
import { Documentation } from "express-zod-api";
const yamlString = new Documentation({
routing, // the same routing and config that you use to start the server
config,
version: "1.2.3",
title: "Example API",
serverUrl: "https://example.com",
composition: "inline", // optional, or "components" for keeping schemas in a separate dedicated section using refs
// descriptions: { positiveResponse, negativeResponse, requestParameter, requestBody } // check out these features
}).getSpecAsYaml();
You can add descriptions and examples to your endpoints, their I/O schemas and their properties. It will be included into the generated documentation of your API. Consider the following example:
import { defaultEndpointsFactory } from "express-zod-api";
const exampleEndpoint = defaultEndpointsFactory.build({
shortDescription: "Retrieves the user.", // <—— this becomes the summary line
description: "The detailed explanaition on what this endpoint does.",
input: z
.object({
id: z.number().describe("the ID of the user"),
})
.example({
id: 123,
}),
// ..., similarly for output and middlewares
});
See the example of the generated documentation here
When generating documentation, you may find it necessary to classify endpoints into groups. For this, the
possibility of tagging endpoints is provided. In order to achieve the consistency of tags across all endpoints, the
possible tags should be declared in the configuration first and another instantiation approach of the
EndpointsFactory is required. Consider the following example:
import {
createConfig,
EndpointsFactory,
defaultResultHandler,
} from "express-zod-api";
const config = createConfig({
// ..., use the simple or the advanced syntax:
tags: {
users: "Everything about the users",
files: {
description: "Everything about the files processing",
url: "https://example.com",
},
},
});
// instead of defaultEndpointsFactory use the following approach:
const taggedEndpointsFactory = new EndpointsFactory({
resultHandler: defaultResultHandler, // or use your custom one
config, // <—— supply your config here
});
const exampleEndpoint = taggedEndpointsFactory.build({
// ...
tag: "users", // or tags: ["users", "files"]
});
You can customize handling rules for your schemas in Documentation and Integration. Use the .brand() method on your
schema to make it special and distinguishable for the library in runtime. Using symbols is recommended for branding.
After that utilize the brandHandling feature of both constructors to declare your custom implementation. In case you
need to reuse a handling rule for multiple brands, use the exposed types Depicter and Producer.
import ts from "typescript";
import { z } from "zod";
import {
Documentation,
Integration,
Depicter,
Producer,
} from "express-zod-api";
const myBrand = Symbol("MamaToldMeImSpecial"); // I recommend to use symbols for this purpose
const myBrandedSchema = z.string().brand(myBrand);
const ruleForDocs: Depicter = (
schema: typeof myBrandedSchema, // you should assign type yourself
{ next, path, method, isResponse }, // handle a nested schema using next()
) => {
const defaultDepiction = next(schema.unwrap()); // { type: string }
return { summary: "Special type of data" };
};
const ruleForClient: Producer = (
schema: typeof myBrandedSchema, // you should assign type yourself
{ next, isResponse, serializer }, // handle a nested schema using next()
) => ts.factory.createKeywordTypeNode(ts.SyntaxKind.BooleanKeyword);
new Documentation({
/* config, routing, title, version */
brandHandling: { [myBrand]: ruleForDocs },
});
new Integration({
/* routing */
brandHandling: { [myBrand]: ruleForClient },
});
There are some well-known issues and limitations, or third party bugs that cannot be fixed in the usual way, but you should be aware of them.
Despite being supported by the library, z.coerce.* schema
does not work intuitively.
Please be aware that z.coerce.number() and z.number({ coerce: true }) (being typed not well) still will NOT allow
you to assign anything but number. Moreover, coercive schemas are not fail-safe and their methods .isOptional() and
.isNullable() are buggy. If possible, try to avoid using this type
of schema. This issue will NOT be fixed in
Zod version 3.x.
The schema validator removes excessive properties by default. However, Typescript does not yet display errors in this case during development. You can achieve this verification by assigning the output schema to a constant and reusing it in forced type of the output:
import { z } from "zod";
const output = z.object({
anything: z.number(),
});
endpointsFactory.build({
methods,
input,
output,
handler: async (): Promise<z.input<typeof output>> => ({
anything: 123,
excessive: "something", // error TS2322, ok!
}),
});
If you have a question or idea, or you found a bug, or vulnerability, or security issue, or want to make a PR: please refer to Contributing Guidelines.
FAQs
A Typescript framework to help you get an API server up and running with I/O schema validation and custom middlewares in minutes.
The npm package express-zod-api receives a total of 4,150 weekly downloads. As such, express-zod-api popularity was classified as popular.
We found that express-zod-api demonstrated a healthy version release cadence and project activity because the last version was released less than a year ago. It has 1 open source maintainer collaborating on the project.
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