Rename js snippets

snippets/js/s/deep-equality-comparison.md

@@ -0,0 +1,44 @@
+---
+title: Check object equality
+type: snippet
+language: javascript
+tags: [object,array,type,recursion]
+cover: dying-flowers
+dateModified: 2021-10-13T19:29:39+02:00
+---
+
+Performs a deep comparison between two values to determine if they are equivalent.
+
+- Check if the two values are identical.
+- Check if both values are `Date` objects with the same time, using `Date.prototype.getTime()`.
+- Check if both values are non-object values with an equivalent value (strict comparison).
+- Check if only one value is `null` or `undefined` or if their prototypes differ.
+- If none of the above conditions are met, use `Object.keys()` to check if both values have the same number of keys.
+- Use `Array.prototype.every()` to check if every key in `a` exists in `b` and if they are equivalent by calling `equals()` recursively.
+
+```js
+const equals = (a, b) => {
+  if (a === b) return true;
+
+  if (a instanceof Date && b instanceof Date)
+    return a.getTime() === b.getTime();
+
+  if (!a || !b || (typeof a !== 'object' && typeof b !== 'object'))
+    return a === b;
+
+  if (a.prototype !== b.prototype) return false;
+
+  const keys = Object.keys(a);
+  if (keys.length !== Object.keys(b).length) return false;
+
+  return keys.every(k => equals(a[k], b[k]));
+};
+```
+
+```js
+equals(
+  { a: [2, { e: 3 }], b: [4], c: 'foo' },
+  { a: [2, { e: 3 }], b: [4], c: 'foo' }
+); // true
+equals([1, 2, 3], { 0: 1, 1: 2, 2: 3 }); // true
+```