middlewarify
Advanced tools
Middleware pattern implementation, robust, easy, fast. You can add two types
of middleware, a single queue type using the keyword use() or a Before/After
type using before() and after() hooks.
npm install middlewarify --save
Creating a middleware:
const middlewarify = require('middlewarify');
// this is the main callback of your middleware,
// it will be the last callback to be invoked.
function createTask(data) {
console.log('createTask Final Fn to be invoked');
return true;
}
const tasks = {};
// Make the'create' Middleware Container.
middlewarify.make(tasks, 'create', createTask);
module.exports = tasks;
...Add middleware
// ... somewhere far far away in another file
const tasks = require('./tasks');
// add middleware to the 'create' operation
tasks.create.use(function(data) {
console.log('middleware 1');
data.newAttr = 2;
});
// Add a second middleware to the 'create' operation
tasks.create.use(function(data) {
console.log('middleware 2. Title:', data.title);
data.secondAttr = 3;
});
... Invoke all the middleware
// ... Invoking them all together
const result = tasks.create(data);
// The middleware are invoked in sequence and output:
// "middleware 1"
// "middleware 2"
// "createTask Final Fn to be invoked"
console.log(result);
// prints: true
The middlewarify.make() method will apply the middleware pattern to an
Object's property, this property is the Middleware Container.
// create a Middleware Container
const crud = {};
middlewarify.make(crud, 'create');
This example has created the Middleware Container create in the object
crud. crud.create() is a function that will invoke all the middleware.
You can pass a third argument, the optMainCallback, a Function. This will
be the Main callback of your middleware, the result returned from that
function will be the returning value of the Middleware Container:
const val = crud.create();
// val is passed from the Main callback.
optOptions defines behavior. Both optOptions and optMainCallback are
optional. You can pass options as a third argument, read on for
examples and what are the available options.
make() accepts the following options:
async type: Boolean, default: false Enables asynchronous invocation
of all middleware. Every middleware will be invoked asynchronously and the
final returning value will be a promise.beforeAfter type: Boolean, default: false If set to true the
Before/After hooks will be used instead of the single queue use hook,
which is the default.
View the Before After example.catchAll type Function, default: null If defined all errors will
be piped to this callback, useful when Middleware is used as an
Express middleware.The Middleware Container by default exposes a use hook so you can add any
number of middleware. use() accepts any number of parameters as long they
are of type Function or Array of Functions. When the Before/After flag is
enabled use is no longer available and instead you get before, after and
last hooks. All hook types accept the same argument types and patterns as
described bellow:
// create the Middleware Container
const crud = {};
middlewarify.make(crud, 'create', fnFinal);
// add 3 middleware functions
crud.create.use([fn1, fn2], fn3);
// then add another one
crud.create.use(fn4);
In the above example we added 4 middleware before the final method fnFinal
will be invoked. A FIFO queue is implemented so the order of execution will be:
fn1()fn2()fn3()fn4()fnFinal()All middleware get invoked with the arguments that the Middleware Container was invoked with. The same number or arguments, the exact same references:
app.connect.use(function(req) {
req.a === 1; // true
req.a++;
});
app.connect.use(function(req) {
req.a === 2; // true
});
const req = { a: 1 };
app.connect(req);
When the option async: true is defined, all middleware get invoked
asynchronously. You can return a Promise from your middleware and
Middlewarify will wait for its resolution before passing control to the
next one.
// create an async Middleware Container
const crud = {};
middlewarify.make(crud, 'create', fnFinal, { async: true });
crud.create.before(async () {
await fs.read();
});
The Middleware Container is a function that accepts any number of arguments.
Any argument passed to the Middleware Container will also be passed to all middleware.
const crud = {};
middlewarify.make(crud, 'create');
// run all middleware
crud.create({ a: 1, b: 2 }, 'bar');
Arguments of all middleware will get:
crud.create.use(function(arg1, arg2) {
arg1 === { a: 1, b: 2 }; // true
arg2 === 'bar'; // true
});
When invoked, the Middleware Container will return the execution outcome.
To handle any errors thrown, you simply have to wrap it in a try catch
block unless you have defined a catchAll error handler. In that case
the catchAll error handler will intercept any and all errors.
try {
const retVal = crud.create(arg1, arg2, fn1);
} catch (ex) {
// handle the error...
console.log('Error:', ex);
}
To use the Before/After/Last hook types all you need to do is pass the
{beforeAfter: true} option to Middlewarify's make() method.
When using the beforeAfter option instead of the typical use() method
three new hooks are created on the resulting Middleware Container:
midd.before() Hook functions to be invoked before the main
middleware function.midd.after() Hook functions to be invoked after the main middleware
function.midd.last() Hook functions to be invoked last, after the main
middleware and all middleware functions have been executed.All added hooks are invoked in the order they were added.
const middlewarify = require('middlewarify');
const tasks = (module.exports = {});
// This is the main callback of your middleware,
// it will be invoked after all 'before' middleware finish
// and before any 'after' middleware.
function createTask() {
console.log('Invoked Second');
return 999;
}
// Make the'create' Middleware Container using before/after hooks
middlewarify.make(tasks, 'create', createTask, { beforeAfter: true });
/** ... */
// add a before hook
tasks.create.before(function() {
console.log('Invoked First');
});
// add an after hook
tasks.create.after(function() {
console.log('Invoked Third');
});
// add an always LAST hook, will always invoke last
task.create.last(function() {
console.log('Will always invoke last');
});
/** ... */
// invoke all middleware
tasks.create().then(
function(val) {
// at this point all middleware have finished.
console.log(val); // 999
},
function(err) {
// handle error
},
);
If your middleware if a Before / After type, then all .after() and .last()
hooks will receive an extra argument representing the returned value of
the main callback:
middlewarify.make(crud, 'create', function(arg1, arg2) {
return 'abc';
});
crud.create.after(function(arg1, arg2, val) {
console.log(val); // prints 'abc'
});
crud.create(1, 2);
All After & Last hooks may alter the return result as long as they return any
type of value except undefined:
middlewarify.make(crud, 'create', function() {
return 'abc';
});
crud.create.after(function(result) {
// return an altered outcome
return 'def';
});
crud.create().then(function(result) {
console.log(result); // prints "def"
});
async to enable the asynchronous invocation..last() middleware type in beforeAfter family.catchAll option for cases where invocations have no error handlers..after() hooks.Promise.try()Copyright Thanasis Polychronakis, licensed under the MIT License.
FAQs
Apply the middleware pattern to any function.
The npm package middlewarify receives a total of 22 weekly downloads. As such, middlewarify popularity was classified as not popular.
We found that middlewarify demonstrated a not healthy version release cadence and project activity because the last version was released a year ago. It has 1 open source maintainer collaborating on the project.
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