add array#removeFastWithoutKeepingOrder

Author: jrieken

src/vs/base/common/arrays.ts

@@ -46,6 +46,18 @@ export function equals<T>(one: ReadonlyArray<T> | undefined, other: ReadonlyArra
 	return true;
 }
 
+/**
+ * Remove the element at `index` by replacing it with the last element. This is faster than `splice`
+ * but changes the order of the array
+ */
+export function removeFastWithoutKeepingOrder<T>(array: T[], index: number) {
+	const last = array.length - 1;
+	if (index < last) {
+		array[index] = array[last];
+	}
+	array.pop();
+}
+
 /**
  * Performs a binary search algorithm over a sorted array.
  *

src/vs/base/test/common/arrays.test.ts

@@ -6,6 +6,19 @@ import * as assert from 'assert';
 import * as arrays from 'vs/base/common/arrays';
 
 suite('Arrays', () => {
+
+	test('removeFastWithoutKeepingOrder', () => {
+		const array = [1, 4, 5, 7, 55, 59, 60, 61, 64, 69];
+		arrays.removeFastWithoutKeepingOrder(array, 1);
+		assert.deepStrictEqual(array, [1, 69, 5, 7, 55, 59, 60, 61, 64]);
+
+		arrays.removeFastWithoutKeepingOrder(array, 0);
+		assert.deepStrictEqual(array, [64, 69, 5, 7, 55, 59, 60, 61]);
+
+		arrays.removeFastWithoutKeepingOrder(array, 7);
+		assert.deepStrictEqual(array, [64, 69, 5, 7, 55, 59, 60]);
+	});
+
 	test('findFirst', () => {
 		const array = [1, 4, 5, 7, 55, 59, 60, 61, 64, 69];