Rename js snippets

snippets/js/s/function-based-array-difference.md

@@ -0,0 +1,27 @@
+---
+title: Array difference based on function
+type: snippet
+language: javascript
+tags: [array]
+cover: folded-map
+dateModified: 2020-10-22T20:23:47+03:00
+---
+
+Filters out all values from an array for which the comparator function does not return `true`.
+
+- Use `Array.prototype.filter()` and `Array.prototype.findIndex()` to find the appropriate values.
+- Omit the last argument, `comp`, to use a default strict equality comparator.
+
+```js
+const differenceWith = (arr, val, comp = (a, b) => a === b) =>
+  arr.filter(a => val.findIndex(b => comp(a, b)) === -1);
+```
+
+```js
+differenceWith(
+  [1, 1.2, 1.5, 3, 0],
+  [1.9, 3, 0],
+  (a, b) => Math.round(a) === Math.round(b)
+); // [1, 1.2]
+differenceWith([1, 1.2, 1.3], [1, 1.3, 1.5]); // [1.2]
+```