@feugene/mu
Version:
Helpful TS utilities without dependencies
97 lines • 3.57 kB
JavaScript
/**
* Compares the contents of 2 or more objects using strict equality.
*/
import isObject from '../is/isObject.mjs';
export default function equal(origin, ...list) {
let i, l, leftChain, rightChain;
if (!isObject(origin) || list.length === 0) {
throw new Error('Need two or more arguments to compare');
}
function compare2Objects(x, y) {
let p;
// remember that NaN === NaN returns false
// and isNaN(undefined) returns true
// isNumeric(x,y)
if (isNaN(x) && isNaN(y) && typeof x === 'number' && typeof y === 'number') {
return true;
}
// Compare primitives and functions.
// Check if both arguments link to the same object.
// Especially useful on the step where we compare prototypes
if (x === y) {
return true;
}
// Works in case when functions are created in constructor.
// Comparing dates is a common scenario. Another built-ins?
// We can even handle functions passed across iframes
if ((typeof x === 'function' && typeof y === 'function') ||
(x instanceof Date && y instanceof Date) ||
(x instanceof RegExp && y instanceof RegExp) ||
(x instanceof String && y instanceof String) ||
(x instanceof Number && y instanceof Number)) {
return x.toString() === y.toString();
}
// At last checking prototypes as good as we can
if (!(x instanceof Object && y instanceof Object)) {
return false;
}
if (Object.prototype.isPrototypeOf.call(x, y) || Object.prototype.isPrototypeOf.call(y, x)) {
return false;
}
if (x.constructor !== y.constructor) {
return false;
}
if (x.prototype !== y.prototype) {
return false;
}
// Check for infinitive linking loops
if (leftChain.includes(x) || rightChain.includes(y)) {
return false;
}
// Quick checking of one object being a subset of another.
// todo: cache the structure of arguments[0] for performance
for (p in y) {
if (Object.prototype.isPrototypeOf.call(y, p) !== Object.prototype.isPrototypeOf.call(x, p)) {
return false;
}
else if (typeof y[p] !== typeof x[p]) {
return false;
}
}
for (p in x) {
if (Object.prototype.isPrototypeOf.call(y, p) !== Object.prototype.isPrototypeOf.call(x, p)) {
return false;
}
else if (typeof y[p] !== typeof x[p]) {
return false;
}
switch (typeof x[p]) {
case 'object':
case 'function':
leftChain.push(x);
rightChain.push(y);
if (!compare2Objects(x[p], y[p])) {
return false;
}
leftChain.pop();
rightChain.pop();
break;
default:
if (x[p] !== y[p]) {
return false;
}
break;
}
}
return true;
}
for (i = 0, l = list.length; i < l; i++) {
leftChain = []; // @Todo: this can be cached
rightChain = [];
if (!compare2Objects(origin, list[i])) {
return false;
}
}
return true;
}
//# sourceMappingURL=equals.mjs.map