create @automattic/js-utils package and add uniqueBy (Automattic#…

…50263)

* lib: introduce `uniqueBy` helper

extract `uniqueBy` into `js-utils` pkg and use TS

remove comment about `null` and `undefined` values

* package.json: set `sideEffects` to `false`

* tsconfig.json: remove `DOM` and `DOM.Iterable` from lib

* update types

Co-authored-by: sarayourfriend <saram@fastmail.com>

* change version to 1.0.0

Co-authored-by: sarayourfriend <saram@fastmail.com>

packages/js-utils/CHANGELOG.md

@@ -0,0 +1,3 @@
+## 1.0.0
+
+Add `uniqueBy`

packages/js-utils/README.md

@@ -0,0 +1,3 @@
+# JavaScript utils
+
+This is a collection of general purpose JavaScript utility functions. 

packages/js-utils/jest.config.js

@@ -0,0 +1,3 @@
+module.exports = {
+	preset: '../../test/packages/jest-preset.js',
+};

packages/js-utils/package.json

@@ -0,0 +1,37 @@
+{
+	"name": "@automattic/js-utils",
+	"version": "1.0.0",
+	"description": "General purpose Javascript utility functions",
+	"homepage": "https://github.com/Automattic/wp-calypso",
+	"license": "GPL-2.0-or-later",
+	"author": "Automattic Inc.",
+	"sideEffects": false,
+	"main": "dist/cjs/index.js",
+	"module": "dist/esm/index.js",
+	"calypso:src": "src/index.ts",
+	"repository": {
+		"type": "git",
+		"url": "git+https://github.com/Automattic/wp-calypso.git",
+		"directory": "packages/js-utils"
+	},
+	"files": [
+		"dist",
+		"src"
+	],
+	"types": "dist/types",
+	"publishConfig": {
+		"access": "public"
+	},
+	"bugs": {
+		"url": "https://github.com/Automattic/wp-calypso/issues"
+	},
+	"scripts": {
+		"clean": "tsc --build ./tsconfig.json ./tsconfig-cjs.json --clean && npx rimraf dist",
+		"build": "tsc --build ./tsconfig.json ./tsconfig-cjs.json",
+		"prepack": "yarn run clean && yarn run build",
+		"watch": "tsc --build ./tsconfig.json --watch"
+	},
+	"dependencies": {
+		"tslib": "^2.1.0"
+	}
+}

packages/js-utils/src/index.ts

@@ -0,0 +1 @@
+export { default as uniqueBy } from './unique-by';

packages/js-utils/src/test/unique-by.js

@@ -0,0 +1,55 @@
+/**
+ * Internal dependencies
+ */
+import uniqueBy from '../unique-by';
+
+describe( 'uniqueBy()', () => {
+	test( 'should remove duplicate values by identity by default (numbers)', () => {
+		const values = [ 1, 2, 3, 1, 2, 4 ];
+		expect( uniqueBy( values ) ).toEqual( [ 1, 2, 3, 4 ] );
+	} );
+
+	test( 'should remove duplicate values by identity by default (strings)', () => {
+		const values = [ 'a', 'b', 'c', 'd', 'a', 'b' ];
+		expect( uniqueBy( values ) ).toEqual( [ 'a', 'b', 'c', 'd' ] );
+	} );
+
+	test( 'should remove duplicate values by identity by default (mixed numbers & strings)', () => {
+		const values = [ 1, 2, 'a', 'b', 1, 2, 'c', 'a' ];
+		expect( uniqueBy( values ) ).toEqual( [ 1, 2, 'a', 'b', 'c' ] );
+	} );
+
+	test( 'should be able to handle `null` and `undefined` values', () => {
+		const values = [ null, null, undefined, undefined ];
+		expect( uniqueBy( values ) ).toEqual( [ null, undefined ] );
+	} );
+
+	test( 'should not remove anything if there are no duplicates', () => {
+		const values = [ 1, 2, 'a', 'b' ];
+		expect( uniqueBy( values ) ).toEqual( [ 1, 2, 'a', 'b' ] );
+	} );
+
+	test( 'should accept a custom compare function (String.trim)', () => {
+		const values = [ 'a', 'a ', ' a ', ' a', '  a' ];
+		const compare = ( a, b ) => a.trim() === b.trim();
+		expect( uniqueBy( values, compare ) ).toEqual( [ 'a' ] );
+	} );
+
+	test( 'should accept a custom compare function (parseInt)', () => {
+		const values = [ 1, '1', 2, 3, '3' ];
+		const compare = ( a, b ) => parseInt( a ) === parseInt( b );
+		expect( uniqueBy( values, compare ) ).toEqual( [ 1, 2, 3 ] );
+	} );
+
+	test( 'should accept a custom compare function (objects)', () => {
+		const values = [ { ID: 1 }, { ID: 1 }, { ID: 2 }, { ID: 3 } ];
+		const compare = ( a, b ) => a.ID === b.ID;
+		expect( uniqueBy( values, compare ) ).toEqual( [ { ID: 1 }, { ID: 2 }, { ID: 3 } ] );
+	} );
+
+	test( 'should return a new (shallow) array', () => {
+		const values = [ 1, '2', { ID: 1 } ];
+		expect( uniqueBy( values ) ).not.toBe( values );
+		expect( uniqueBy( values )[ 2 ] ).toBe( values[ 2 ] );
+	} );
+} );

packages/js-utils/src/unique-by.ts

@@ -0,0 +1,10 @@
+const defaultCompare = ( a: any, b: any ): boolean => a === b;
+
+function uniqueBy< T >( arr: T[], fn: ( a: T, b: T ) => boolean = defaultCompare ): T[] {
+	return arr.reduce( ( acc, v ) => {
+		if ( ! acc.some( ( x: any ) => fn( v, x ) ) ) acc.push( v );
+		return acc;
+	}, [] as T[] );
+}
+
+export default uniqueBy;

packages/js-utils/tsconfig-cjs.json

@@ -0,0 +1,11 @@
+{
+	"extends": "./tsconfig",
+	"compilerOptions": {
+		"module": "commonjs",
+		"declaration": false,
+		"declarationDir": null,
+		"outDir": "dist/cjs",
+		"composite": false,
+		"incremental": true
+	}
+}

packages/js-utils/tsconfig.json

@@ -0,0 +1,29 @@
+{
+	"compilerOptions": {
+		"target": "ES5",
+		"lib": [ "ESNext" ],
+		"baseUrl": ".",
+		"module": "esnext",
+		"allowJs": false,
+		"jsx": "react",
+		"declaration": true,
+		"declarationDir": "dist/types",
+		"outDir": "dist/esm",
+		"rootDir": "src",
+		"strict": true,
+		"noUnusedLocals": true,
+		"noUnusedParameters": true,
+		"noImplicitReturns": true,
+		"noFallthroughCasesInSwitch": true,
+		"moduleResolution": "node",
+		"esModuleInterop": true,
+		"forceConsistentCasingInFileNames": true,
+		"typeRoots": [ "../../node_modules/@types" ],
+		"types": [ "node" ],
+		"noEmitHelpers": true,
+		"importHelpers": true,
+		"composite": true
+	},
+	"include": [ "src" ],
+	"exclude": [ "**/test/*" ]
+}

packages/tsconfig.json

@@ -15,6 +15,7 @@
 		{ "path": "./data-stores" },
 		{ "path": "./domain-picker" },
 		{ "path": "./i18n-utils" },
+		{ "path": "./js-utils" },
 		{ "path": "./language-picker" },
 		{ "path": "./languages" },
 		{ "path": "./launch" },