add uniques.js

src/lib/uniques.js

@@ -0,0 +1,22 @@
+export default function uniques (list, iteratee, transform = false) {
+	if (!Array.isArray(list)) {
+		console.error('LayerCake error: Input value to `uniques` must be a list.');
+		return null;
+	};
+	const ll = list.length;
+	const iterater = typeof iteratee === 'function';
+	const key = typeof iteratee !== 'undefined';
+	const seen = [];
+	const result = [];
+	for (let i = 0; i < ll; i++) {
+		const d = list[i];
+		const computed = iterater ? iteratee(d) : key === true ? d[iteratee] : d;
+		if (!seen.includes(computed)) {
+			seen.push(computed);
+			if (transform === false) {
+				result.push(d);
+			}
+		}
+	}
+	return transform === false ? result : seen;
+}

test/uniques.js

@@ -0,0 +1,47 @@
+/* globals describe it */
+import uniques from '../src/lib/uniques.js';
+import * as assert from 'assert';
+
+const name = 'uniques';
+
+const tests = [
+	{ args: [0], expected: null },
+	{ args: [[0]], expected: [0] },
+	{ args: [[0, 0, 1]], expected: [0, 1] },
+	{ args: [['a', 'b', 'b', 'c']], expected: ['a', 'b', 'c'] },
+	{ args: [['a', 1, 'b', 1]], expected: ['a', 1, 'b'] },
+	{
+		args: [
+			[{x: 1, b: 2}, {x: 1, b: 3}, {x: 2, b: 4}],
+			'x'
+		],
+		expected: [{x: 1, b: 2}, {x: 2, b: 4}]
+	},
+	{
+		args: [
+			[{x: 1, b: 2}, {x: 1, b: 3}, {x: 2, b: 4}],
+			'x',
+			true
+		],
+		expected: [1, 2]
+	},
+	{
+		args: [
+			[{x: 1, b: 2}, {x: 1, b: 3}, {x: 2, b: 4}],
+			d => d.x,
+			true
+		],
+		expected: [1, 2]
+	}
+];
+
+describe(name, function () {
+	tests.forEach(test => {
+		describe(JSON.stringify(test.args), function () {
+			it(`should equal ${JSON.stringify(test.expected)}`, function () {
+				const actual = uniques(...test.args);
+				assert.deepStrictEqual(actual, test.expected);
+			});
+		});
+	});
+});