feat(collections): implement sortBy (#1069)

collections/sort_by.ts

@@ -0,0 +1,49 @@
+// Copyright 2018-2021 the Deno authors. All rights reserved. MIT license.
+
+/**
+ * Returns all elements in the given collection, sorted by their result using the given selector
+ *
+ * Example:
+ *
+ * ```ts
+ * import { sortBy } from "./sort_by.ts"
+ *
+ * const people = [
+ *     { name: 'Anna', age: 34 },
+ *     { name: 'Kim', age: 42 },
+ *     { name: 'John', age: 23 },
+ * ]
+ * const sortedByAge = sortBy(people, it => it.age)
+ *
+ * console.assert(sortedByAge === [
+ *     { name: 'John', age: 23 },
+ *     { name: 'Anna', age: 34 },
+ *     { name: 'Kim', age: 42 },
+ * ])
+ * ```
+ */
+export function sortBy<T>(
+  array: Array<T>,
+  selector:
+    | ((el: T) => number)
+    | ((el: T) => string)
+    | ((el: T) => bigint)
+    | ((el: T) => Date),
+): Array<T> {
+  const ret = Array.from(array);
+
+  return ret.sort((a, b) => {
+    const selectedA = selector(a);
+    const selectedB = selector(b);
+
+    if (selectedA > selectedB) {
+      return 1;
+    }
+
+    if (selectedA < selectedB) {
+      return -1;
+    }
+
+    return 0;
+  });
+}

collections/sort_by_test.ts

@@ -0,0 +1,104 @@
+// Copyright 2018-2021 the Deno authors. All rights reserved. MIT license.
+
+import { assertEquals } from "../testing/asserts.ts";
+import { sortBy } from "./sort_by.ts";
+
+function sortByTest<T>(
+  input: [
+    Array<T>,
+    | ((el: T) => number)
+    | ((el: T) => string)
+    | ((el: T) => bigint)
+    | ((el: T) => Date),
+  ],
+  expected: Array<T>,
+  message?: string,
+) {
+  const actual = sortBy(...input);
+  assertEquals(actual, expected, message);
+}
+
+Deno.test({
+  name: "[collections/sortBy] no mutation",
+  fn() {
+    const array = ["a", "abc", "ba"];
+    sortBy(array, (it) => it.length);
+
+    assertEquals(array, ["a", "abc", "ba"]);
+  },
+});
+
+Deno.test({
+  name: "[collections/sortBy] empty input",
+  fn() {
+    sortByTest(
+      [[], () => 5],
+      [],
+    );
+  },
+});
+
+Deno.test({
+  name: "[collections/sortBy] identity selector",
+  fn() {
+    sortByTest(
+      [
+        [2, 3, 1],
+        (it) => it,
+      ],
+      [1, 2, 3],
+    );
+  },
+});
+
+Deno.test({
+  name: "[collections/sortBy] sortings",
+  fn() {
+    const testArray = [
+      { name: "benchmark", stage: 3 },
+      { name: "test", stage: 2 },
+      { name: "build", stage: 1 },
+      { name: "deploy", stage: 4 },
+    ];
+
+    sortByTest(
+      [
+        testArray,
+        (it) => it.stage,
+      ],
+      [
+        { name: "build", stage: 1 },
+        { name: "test", stage: 2 },
+        { name: "benchmark", stage: 3 },
+        { name: "deploy", stage: 4 },
+      ],
+    );
+    sortByTest(
+      [
+        testArray,
+        (it) => it.name,
+      ],
+      [
+        { name: "benchmark", stage: 3 },
+        { name: "build", stage: 1 },
+        { name: "deploy", stage: 4 },
+        { name: "test", stage: 2 },
+      ],
+    );
+    sortByTest(
+      [
+        [
+          "February 1, 2022",
+          "December 17, 1995",
+          "June 12, 2012",
+        ],
+        (it) => new Date(it),
+      ],
+      [
+        "December 17, 1995",
+        "June 12, 2012",
+        "February 1, 2022",
+      ],
+    );
+  },
+});