the most reliable/idiot-proof equality is by avoiding classes altogether; stick
with plain json-objects and compare their canonical-json-representation like
this real-world example [1]:
```
/*jslint devel*/
(function () {
"use strict";
var jsonStringifyCanonical;
jsonStringifyCanonical = function (obj, replacer, space) {
/*
* this function will JSON.stringify <obj>,
* with object-keys sorted and circular-references removed
*/
var circularSet;
var stringify;
var tmp;
stringify = function (obj) {
/*
* this function will recursively JSON.stringify obj,
* with object-keys sorted and circular-references removed
*/
// if obj is not an object or function,
// then JSON.stringify as normal
if (!(
obj
&& typeof obj === "object"
&& typeof obj.toJSON !== "function"
)) {
return JSON.stringify(obj);
}
// ignore circular-reference
if (circularSet.has(obj)) {
return;
}
circularSet.add(obj);
// if obj is an array, then recurse its items
if (Array.isArray(obj)) {
tmp = "[" + obj.map(function (obj) {
// recurse
tmp = stringify(obj);
return (
typeof tmp === "string"
? tmp
: "null"
);
}).join(",") + "]";
circularSet.delete(obj);
return tmp;
}
// if obj is not an array,
// then recurse its items with object-keys sorted
tmp = "{" + Object.keys(obj).sort().map(function (key) {
// recurse
tmp = stringify(obj[key]);
if (typeof tmp === "string") {
return JSON.stringify(key) + ":" + tmp;
}
}).filter(function (obj) {
return typeof obj === "string";
}).join(",") + "}";
circularSet.delete(obj);
return tmp;
};
circularSet = new Set();
return JSON.stringify((
(typeof obj === "object" && obj)
// recurse
? JSON.parse(stringify(obj))
: obj
), replacer, space);
};
// true
console.assert(
// {"data":{"x":1,"y":2,"z":3},"meta":{"label":"point #13"}}
jsonStringifyCanonical({
data: {x: 1, y: 2, z: 3},
meta: {label: "point #32"}
})
// === {"data":{"x":1,"y":2,"z":3},"meta":{"label":"point #13"}}
=== jsonStringifyCanonical({
meta: {label: "point #32"},
data: {z: 3, y: 2, x: 1}
})
);
}());
```
[1] testing aa “==“ b by comparing their canonical json-representation
https://github.com/kaizhu256/node-utility2/blob/2018.12.30/test.js#L2903
<https://github.com/kaizhu256/node-utility2/blob/2018.12.30/test.js#L2903>
https://github.com/kaizhu256/node-utility2/blob/2018.12.30/lib.utility2.js#L2760
<https://github.com/kaizhu256/node-utility2/blob/2018.12.30/lib.utility2.js#L2760>
> On 18 Jan 2019, at 3:39 PM, Isiah Meadows <[email protected]> wrote:
>
> Yeah, I agree. I'd suggest overloading `==`, but that'd risk serious web
> compat issues, especially if `null`/`undefined` aren't special-cased. I feel
> an `equals` instance method added to all builtins and an `Object.equals`
> attempting that method first before performing a shallow object comparison
> would be the best solution.
> On Fri, Jan 18, 2019 at 15:24 Jordan Harband <[email protected]
> <mailto:[email protected]>> wrote:
> It's pretty important that the meaning `===` not be able to change.
>
> On Fri, Jan 18, 2019 at 10:33 AM ViliusCreator <[email protected]
> <mailto:[email protected]>> wrote:
> What about having Symbol.equals?
>
> For example, for now this is what it does:
>
> ```js
>
> class Position {
> constructor(o) {
> this.x = o.x instanceof Number ? o.x : 0
>
> this.y = o.y instanceof Number ? o.y : 0
>
> this.z = o.z instanceof Number ? o.z : 0
> }
> }
> console.log(new Position({x: 10, y: 10, z: 10}) === new Position({x: 10, y:
> 10, z: 10})
>
> ```
> Output is of course, false.
> With `Symbol.equals`, we could make it easier, instead of
> `instance.equals(otherInstance)`.
>
>
>
> For example:
>
> ```js
>
> class Position {
>
> [Symbol.equals](oIn) {
> return oIn.x === this.x && oIn.y === this.y && oIn.z === this.z
> }
> constructor(o) {
> this.x = o.x instanceof Number ? o.x : 0
>
> this.y = o.y instanceof Number ? o.y : 0
>
> this.z = o.z instanceof Number ? o.z : 0
> }
> }
> console.log(new Position({x: 10, y: 10, z: 10}) === new Position({x: 10, y:
> 10, z: 10})
>
> ```
> Now output would be true.
>
> This would save most of the time, instead of writing .equals and then
> surrounding everything with ().
>
>
>
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