36 lines
1.3 KiB
Markdown
36 lines
1.3 KiB
Markdown
---
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title: equals
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tags: object,array,type,advanced
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firstSeen: 2018-01-15T18:34:11+02:00
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lastUpdated: 2020-10-22T20:23:47+03:00
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---
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Performs a deep comparison between two values to determine if they are equivalent.
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- Check if the two values are identical, if they are both `Date` objects with the same time, using `Date.prototype.getTime()` or if they are both non-object values with an equivalent value (strict comparison).
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- Check if only one value is `null` or `undefined` or if their prototypes differ.
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- If none of the above conditions are met, use `Object.keys()` to check if both values have the same number of keys.
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- Use `Array.prototype.every()` to check if every key in `a` exists in `b` and if they are equivalent by calling `equals()` recursively.
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```js
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const equals = (a, b) => {
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if (a === b) return true;
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if (a instanceof Date && b instanceof Date)
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return a.getTime() === b.getTime();
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if (!a || !b || (typeof a !== 'object' && typeof b !== 'object'))
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return a === b;
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if (a.prototype !== b.prototype) return false;
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let keys = Object.keys(a);
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if (keys.length !== Object.keys(b).length) return false;
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return keys.every(k => equals(a[k], b[k]));
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};
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```
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```js
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equals(
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{ a: [2, { e: 3 }], b: [4], c: 'foo' },
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{ a: [2, { e: 3 }], b: [4], c: 'foo' }
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); // true
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equals([1, 2, 3], { 0: 1, 1: 2, 2: 3 }); // true
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```
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