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

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

	const arr = [1, 2, 3];
	const iter = arr[Symbol.iterator]();
	test('array iterator first', iter.next().value, 1);
	test('array iterator second', iter.next().value, 2);
	test('array iterator third', iter.next().value, 3);
	test('array iterator done', iter.next().done, true);

	const str = 'abc';
	const strIter = str[Symbol.iterator]();
	test('string iterator first', strIter.next().value, 'a');
	test('string iterator second', strIter.next().value, 'b');
	test('string iterator third', strIter.next().value, 'c');
	test('string iterator done', strIter.next().done, true);

	const map = new Map([['a', 1], ['b', 2]]);
	const mapIter = map.entries();
	testDeep('map entries first', mapIter.next().value, ['a', 1]);
	testDeep('map entries second', mapIter.next().value, ['b', 2]);

	const set = new Set([1, 2, 3]);
	const setIter = set.values();
	test('set values first', setIter.next().value, 1);
	test('set values second', setIter.next().value, 2);

	let forOfSum = 0;
	for (const n of [1, 2, 3]) {
	forOfSum += n;
	}
	test('for-of array', forOfSum, 6);

	let forOfStr = '';
	for (const c of 'hi') {
	forOfStr += c;
	}
	test('for-of string', forOfStr, 'hi');

	const custom = {
	data: [10, 20, 30],
	[Symbol.iterator]() {
	let i = 0;
	return {
	next: () => {
	if (i < this.data.length) {
	return { value: this.data[i++], done: false };
	}
	return { done: true };
	}
	};
	}
	};

	let customSum = 0;
	for (const n of custom) {
	customSum += n;
	}
	test('custom iterator', customSum, 60);

	summary();