functions.js
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functions.js
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	import { test, summary } from './helpers.js';

	console.log('Function Tests\n');

	function add(a, b) {
	return a + b;
	}
	test('function declaration', add(2, 3), 5);

	const multiply = function(a, b) {
	return a * b;
	};
	test('function expression', multiply(3, 4), 12);

	const arrow = (a, b) => a - b;
	test('arrow function', arrow(10, 3), 7);

	const arrowSingle = x => x * 2;
	test('arrow single param', arrowSingle(5), 10);

	const arrowBlock = (a, b) => {
	const sum = a + b;
	return sum * 2;
	};
	test('arrow block body', arrowBlock(2, 3), 10);

	function defaultParam(a, b = 10) {
	return a + b;
	}
	test('default param used', defaultParam(5), 15);
	test('default param overridden', defaultParam(5, 3), 8);

	function restParams(first, ...rest) {
	return first + rest.length;
	}
	test('rest params', restParams(1, 2, 3, 4), 4);

	function spreadCall(a, b, c) {
	return a + b + c;
	}
	test('spread in call', spreadCall(...[1, 2, 3]), 6);

	const obj = {
	value: 100,
	getValue() {
	return this.value;
	}
	};
	test('method this', obj.getValue(), 100);

	const arrowThis = {
	value: 50,
	getArrow() {
	return (() => this.value)();
	}
	};
	test('arrow this binding', arrowThis.getArrow(), 50);

	function outer() {
	let x = 10;
	return function inner() {
	return x;
	};
	}
	test('closure', outer()(), 10);

	const counter = (() => {
	let count = 0;
	return {
	inc() { return ++count; },
	get() { return count; }
	};
	})();
	test('iife closure inc', counter.inc(), 1);
	test('iife closure get', counter.get(), 1);

	function factorial(n) {
	if (n <= 1) return 1;
	return n * factorial(n - 1);
	}
	test('recursion', factorial(5), 120);

	test('function name', add.name, 'add');
	test('function length', add.length, 2);

	function bindTest(greeting) {
	return greeting + ' ' + this.name;
	}
	const boundFn = bindTest.bind({ name: 'World' });
	test('bind', boundFn('Hello'), 'Hello World');

	test('call', bindTest.call({ name: 'Call' }, 'Hi'), 'Hi Call');
	test('apply', bindTest.apply({ name: 'Apply' }, ['Hey']), 'Hey Apply');

	const gen = (function() {
	const fns = [];
	for (let i = 0; i < 3; i++) {
	fns.push(() => i);
	}
	return fns;
	})();
	test('closure in loop 0', gen[0](), 0);
	test('closure in loop 1', gen[1](), 1);
	test('closure in loop 2', gen[2](), 2);

	summary();

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