JSONSon

Utility lib to convert raw JSON.parse output to declared types.

Usage

There are two ways how JSONSon can be imported and used.

Global:

<script type="module" src="./JSONSon.js"></script>
<script>

let schema = new JSON.Son({ ... });

</script>

Within a module:

<script type="module">

import JSONSon from './JSONSon.js';
let schema = new JSONSon({ ... });

</script>

Static functions

JSONSon.prototype.constructor(type)

Create an instance of JSONSon storing type within private property this._type. This object can be safely converted to a JSON if you want to transfer schema itself: JSON.stringify(new JSONSon(Boolean)).

JSONSon.prototype.make(data)

Process and convert values of data to types according to declarations in this._type.

JSONSon.prototype.parse(json)

Parse string value json and invoke JSONSon.prototype.make internally.

static JSONSon.make(type, data)

There's no need to instantiate a JSONSon when you dont need it. You can just call this static alternative function to convert values of data to types according to declarations in type.

static JSONSon.parse(type, json)

There's no need to instantiate a JSONSon when you dont need it. You can just call this static alternative function to parse json and convert its values to types according to declarations in type.

Examples

Primitives

JSONSon.parse('string', '"foo"');
// Result: string primitive "foo" (there's no magic)

new JSONSon('string').parse('"foo"');
// Same as previous

JSONSon.parse('boolean', '1');
// Result: boolean true
// (primitive numeric value 1 converted to boolean true)

JSONSon.parse('boolean', '"0"');
// Result: boolean false
// (primitive string value "0" converted to boolean false)

JSONSon.parse('bigint', '"9007199254740993"');
// Result: bigint 9007199254740993n
// (primitive string value "9007199254740993" converted to bigint)

Converting bigint values

If you need BigInt -> JSON conversion, you should implement your own BigInt.toJSON method first:

BigInt.prototype.toJSON = function () { return this.toString(10); };

Now bigint values can be safely converted to and from JSON:

JSON.stringify(1234n); // -> "1234"
JSON.stringify(Object(5678n)); // -> "5678"
JSONSon.make('bigint', '9007199254740993'); // -> 9007199254740993n
var n = JSONSon.make(BigInt, '9007199254740993'); // -> BigInt {9007199254740993n}
JSON.stringify({ n: n }); // -> { "n": "9007199254740993" }

Arrays

JSONSon.parse(['string'], '[1, "2", 3]');
// Result: Array ["1", "2", "3"]
// (all elements of array are primitive strings)

JSONSon.parse([['number']], '[[1, "2", 3], [4, 5, 6], [7, 8, 9]]'); // 3x3 matrix
// Result: Array [[1, 2, 3], [4, 5, 6], [7, 8, 9]]
// (all elements of nested arrays are primitive numbers)

JSONSon.parse({ 2: 'string' }, '[0, "1", 2]');
// Result: Object { 0: 0, 1: '1', 2: '2' }
// (array converted to an object;
// value of prop '2' converted to string,
// while the rest left as they were)

Objects

var schema = new JSONSon({
    str: 'string',
    num: 'number',
    bool: 'boolean',
    arr: ['number'],
    foo: {
        bar: 'string',
    },
    StringClass: String,
    BigInt: BigInt,
    ololo: 'string', // object props are optional
});
schema.make({
    str: 1234, // becomes string '1234'
    num: '5678', // becomes number 5678
    bool: 90, // becomes true
    arr: [1, '2', 3], // becomes an array of numbers
    foo: { // becomes a sub-object
        bar: 'baz', // becomes a primitive string
    },
    StringClass: 'not primitive', // becomes a String object
    BigInt: '9007199254740993', // becomes a BigInt object
    // ololo: '', // skip
});
/* Result: Object {
    str: '1234',
    num: 5678,
    bool: true,
    arr: [1, 2, 3],
    foo: {
        bar: 'baz',
    },
    StringClass: String {'not primitive'},
    BigInt: BigInt {'9007199254740993'],
} */

Tuples

var schema = new JSONSon([
    'string',
    'boolean',
    'number',
]);
schema.make([
    0, // becomes string '0'
    1, // becomes boolean true
    '2', // this and the rest of elements become numbers
    3,
    4,
]);
/* Result: Array [
    '0',
    true,
    2,
    3,
    4
] */

Classes

// some-geometry-library.js
class Point {
    constructor(x, y) {
        this.x = x;
        this.y = y;
    }
    
    /**
     * Magic method, called by JSON.stringify
     */
    toJSON() {
        return [this.x, this.y]; // return array
    }
    
    /**
     * Magic method, called by JSONSon
     */
    static fromJSON(data) {
        // assuming, that data is array [x, y]
        return new this(data[0], data[1]);
    }
}

// index.js
import { Point } from 'some-geometry-library';

var point = new Point(4, 9); // Point { x: 4, y: 9 }
var json = JSON.stringify(point); // [4, 9]
var schema = new JSONSon(Point);
schema.parse(json);
/* Result: Point {
    x: 4,
    y: 9
} */

Class with extra properties

If the object is an instance of known class, but has extra properties, you can use JSONSon.mix:

// some-geometry-library.js
class Rect {
    constructor(p0, p1) {
        this.p0 = p0;
        this.p1 = p1;
    }
    
    static fromJSON(data) {
        return new this(JSONSon.make(Point, data.p0), JSONSon.make(Point, data.p1));
    }
}

// index.js
import { Rect, Point } from 'some-geometry-library';
var rect = new Rect(new Point(0, 0), new Point(5, 6));

// define extra property:
rect.clickable = true;

var json = JSON.stringify(rect); // {"p0": [0,0], "p1": [5,6], "clickable": true}

JSONSon.parse(Rect, json); // property 'clickable' is lost :(

// But...
var schema = new JSONSon(JSONSon.mix(Rect, {
    clickable: 'boolean', // declare extra property
}));
schema.parse(json);
/* Result: Rect {
    p0: Point {
        x: 0,
        y: 0,
    },
    p1: Point {
        x: 5,
        y: 6,
    },
    clickable: true <-- here it is!
} */

Stringify JSONSon itself

JSONSon class can be safely stringified as JSON:

import { Rect } from 'some-geometry-library';

var schema = new JSONSon({
    str: 'string',
    arr: ['number'],
    foo: {
        bar: 'string',
    },
    StringClass: String,
    BigInt: BigInt,
    
    rect: Rect, // custom imported class
});

var json = JSON.stringify(schema, null, '  ');
/* Result: string `{
  "type": "object",
  "name": "Object",
  "value": {
    "str": "string",
    "arr": [
      "number"
    ],
    "foo": {
      "type": "object",
      "name": "Object",
      "value": {
        "bar": "string"
      }
    },
    "StringClass": {
      "type": "constructor",
      "name": "String"
    },
    "BigInt": {
      "type": "constructor",
      "name": "BigInt"
    },
    "rect": {
      "type": "constructor",
      "name": "Rect"
    }
  }
}` */

Now it can be thansferred for example from server to client and recomposed to live JSONSon:

JSONSon.parse(JSONSon, json);
/* Result: JSONSon {
    _type: {
        ...
        ...
        rect: f Object() <-- WAT???
    }
} */

Type of property 'rect' is wrong now. That's because the other environment doesn't know a custom class named 'Rect'. But there's a workaround. The one should re-implement static method JSONSon.resolveConstructor.

Implement custom JSONSon.resolveConstructor

import { Point, Rect } from 'some-geometry-library';

// You should define a way to resolve constructors
// from its names:
JSONSon.resolveConstructor = (name) => {
    if (name === 'Point') {
        // Since class Point is not exported to window.*,
        // we should pass its constructor from current scope
        return Point;
    }
    if (name === 'Rect') {
        // Since class Rect is not exported to window.*,
        // we should pass its constructor from current scope
        return Rect;
    }
    return window[name];
};

var schema = JSONSon.parse(JSONSon, json);
/* Result: JSONSon {
    _type: {
        ...
        ...
        rect: class Rect <-- It's okay now
    }
} */

var res = schema.parse('{ ... "rect": { "p0": [0,0], "p1": [5,6] } }');
/* Value of res.rect: Rect {
    p0: Point {
        x: 0,
        y: 0,
    },
    p1: Point {
        x: 5,
        y: 6,
    },
} */

Implement magic static method CustomClass.getJSONSonSchema

It is possible to over-declare schema of specific class. For example, you can declare a JSONSon.mix:

// some-geometry-library.js
class Rect {
    constructor(p0, p1) {
        this.p0 = p0;
        this.p1 = p1;
    }
    
    static fromJSON(data) {
        return new this(JSONSon.make(Point, data.p0), JSONSon.make(Point, data.p1));
    }
    
    static getJSONSonSchema() {
        return JSONSon.mix(this, {
            clickable: 'boolean', // declare extra property
        });
    }
}

// index.js

import { Rect, Point } from 'some-geometry-library';

// There's no need to declare JSONSon.mix outside anymore:
var schema = new JSONSon(Rect);

var rect = new Rect(new Point(0, 0), new Point(5, 6));
// define extra property:
rect.clickable = true;

var json = JSON.stringify(rect); // {"p0": [0,0], "p1": [5,6], "clickable": true}

schema.parse(json);
/* Result: Rect {
    p0: Point {
        x: 0,
        y: 0,
    },
    p1: Point {
        x: 5,
        y: 6,
    },
    clickable: true <-- here it is!
} */

Another example (don't do it IRL): you can make all instances of Number to be converted to primitive numbers:

var json = JSON.stringify(1234); // string '1234'
var parsedRaw = JSON.parse(json); // number 1234

JSONSon.parse(Number, json);
// Result: Number {1234}

Number.getJSONSonSchema = () => 'number'; // the magic is here

JSONSon.parse(Number, json);
// Result: number 1234
// (because JSONSon has called Number.getJSONSonSchema
// and got updated schema for an instance:
// primitive number instead of Number class)

Known issues

• ~~When some class overrides its schema with getJSONSonSchema, it ignored within mix~~