feat: add makeBooleanCompareFn

Author: spawnia

package.json

@@ -79,5 +79,5 @@
     "ts-node": "^9.1.1",
     "typescript": "^5.3.3"
   },
-  "packageManager": "yarn@4.4.0"
+  "packageManager": "yarn@4.9.1"
 }

src/array.test.ts

@@ -12,6 +12,7 @@ import {
   toggleElement,
   withoutIndex,
   makeNumberCompareFn,
+  makeBooleanCompareFn,
 } from './array';
 import { Maybe } from './types';
 
@@ -283,6 +284,16 @@ describe('makeNumberCompareFn', () => {
   });
 });
 
+describe('makeBooleanCompareFn', () => {
+  type KeyBoolean = { key: boolean };
+
+  it('creates a compare function that sorts booleans', () => {
+    const compareFn = makeBooleanCompareFn<KeyBoolean>((record) => record.key);
+    const original: Array<KeyBoolean> = [{ key: true }, { key: false }];
+    expect(original.sort(compareFn)).toEqual([{ key: false }, { key: true }]);
+  });
+});
+
 describe('localeCompareStrings', () => {
   it('sorts strings', () => {
     const original: Array<string> = ['c', '', 'a', 'b'];

src/array.ts

@@ -127,6 +127,21 @@ export function makeNumberCompareFn<TSortable>(
   };
 }
 
+/**
+ * Takes a function that maps the values to sort to booleans and returns a compare function that puts `false` before `true`.
+ * Usable in `Array.toSorted` or similar APIs.
+ */
+export function makeBooleanCompareFn<TSortable>(
+  map: (sortable: TSortable) => boolean,
+): (a: TSortable, b: TSortable) => number {
+  return (a, b) => {
+    const mappedA = map(a);
+    const mappedB = map(b);
+
+    return Number(mappedA) - Number(mappedB);
+  };
+}
+
 /**
  * Returns a compare function for values that are string, null or undefined,
  * using `String.prototype.localeCompare`, usable in `Array.toSorted` or similar APIs.