JavaScript ObjectSchema Package
by Nicholas C. Zakas
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Overview
A JavaScript object merge/validation utility where you can define a different merge and validation strategy for each key. This is helpful when you need to validate complex data structures and then merge them in a way that is more complex than Object.assign()
.
Installation
You can install using either npm:
npm install @humanwhocodes/object-schema
Or Yarn:
yarn add @humanwhocodes/object-schema
Usage
Use CommonJS to get access to the ObjectSchema
constructor:
const { ObjectSchema } = require("@humanwhocodes/object-schema");
const schema = new ObjectSchema({
downloads: {
required: true,
merge(value1, value2) {
return value1 + value2;
},
validate(value) {
if (typeof value !== "number") {
throw new Error("Expected downloads to be a number.");
}
}
},
version: {
required: true,
merge(value1, value2) {
return value1.concat(value2);
},
validate(value) {
if (!Array.isArray(value)) {
throw new Error("Expected versions to be an array.");
}
}
}
});
const record1 = {
downloads: 25,
versions: [
"v1.0.0",
"v1.1.0",
"v1.2.0"
]
};
const record2 = {
downloads: 125,
versions: [
"v2.0.0",
"v2.1.0",
"v3.0.0"
]
};
schema.validate(record1);
schema.validate(record2);
const result = schema.merge(record1, record2);
const result = {
downloads: 75,
versions: [
"v1.0.0",
"v1.1.0",
"v1.2.0",
"v2.0.0",
"v2.1.0",
"v3.0.0"
]
};
Tips and Tricks
Remove Keys During Merge
If the merge strategy for a key returns undefined
, then the key will not appear in the final object. For example:
const schema = new ObjectSchema({
date: {
merge() {
return undefined;
},
validate(value) {
Date.parse(value);
}
}
});
const object1 = { date: "5/5/2005" };
const object2 = { date: "6/6/2006" };
const result = schema.merge(object1, object2);
console.log("date" in result);
Requiring Another Key Be Present
If you'd like the presence of one key to require the presence of another key, you can use the requires
property to specify an array of other properties that any key requires. For example:
const schema = new ObjectSchema();
const schema = new ObjectSchema({
date: {
merge() {
return undefined;
},
validate(value) {
Date.parse(value);
}
},
time: {
requires: ["date"],
merge(first, second) {
return second;
},
validate(value) {
}
}
});
schema.validate({
time: "13:45"
});
In this example, even though date
is an optional key, it is required to be present whenever time
is present.
License
BSD 3-Clause