Make Headers iterable

Closes #127, #174.

src/headers.js

@@ -135,4 +135,74 @@ export default class Headers {
 	raw() {
 		return this[MAP];
 	}
+
+	/**
+	 * Get an iterator on keys.
+	 *
+	 * @return  Iterator
+	 */
+	keys() {
+		const keys = [];
+		this.forEach((_, name) => keys.push(name));
+		return new Iterator(keys);
+	}
+
+	/**
+	 * Get an iterator on values.
+	 *
+	 * @return  Iterator
+	 */
+	values() {
+		const values = [];
+		this.forEach(value => values.push(value));
+		return new Iterator(values);
+	}
+
+	/**
+	 * Get an iterator on entries.
+	 *
+	 * @return  Iterator
+	 */
+	entries() {
+		const entries = [];
+		this.forEach((value, name) => entries.push([name, value]));
+		return new Iterator(entries);
+	}
+
+	/**
+	 * Get an iterator on entries.
+	 *
+	 * This is the default iterator of the Headers object.
+	 *
+	 * @return  Iterator
+	 */
+	[Symbol.iterator]() {
+		return this.entries();
+	}
+}
+
+const ITEMS = Symbol('items');
+class Iterator {
+	constructor(items) {
+		this[ITEMS] = items;
+	}
+
+	next() {
+		if (!this[ITEMS].length) {
+			return {
+				value: undefined,
+				done: true
+			};
+		}
+
+		return {
+			value: this[ITEMS].shift(),
+			done: false
+		};
+
+	}
+
+	[Symbol.iterator]() {
+		return this;
+	}
 }

test/test.js

@@ -1131,6 +1131,65 @@ describe('node-fetch', function() {
 		expect(result).to.deep.equal(expected);
 	});
 
+	it('should allow iterating through all headers', function() {
+		var headers = new Headers({
+			a: 1
+			, b: [2, 3]
+			, c: [4]
+		});
+		expect(headers).to.have.property(Symbol.iterator);
+		expect(headers).to.have.property('keys');
+		expect(headers).to.have.property('values');
+		expect(headers).to.have.property('entries');
+
+		var result, expected;
+
+		result = [];
+		for (let [key, val] of headers) {
+			result.push([key, val]);
+		}
+
+		expected = [
+			["a", "1"]
+			, ["b", "2"]
+			, ["b", "3"]
+			, ["c", "4"]
+		];
+		expect(result).to.deep.equal(expected);
+
+		result = [];
+		for (let [key, val] of headers.entries()) {
+			result.push([key, val]);
+		}
+		expect(result).to.deep.equal(expected);
+
+		result = [];
+		for (let key of headers.keys()) {
+			result.push(key);
+		}
+
+		expected = [
+			"a"
+			, "b"
+			, "b"
+			, "c"
+		];
+		expect(result).to.deep.equal(expected);
+
+		result = [];
+		for (let key of headers.values()) {
+			result.push(key);
+		}
+
+		expected = [
+			"1"
+			, "2"
+			, "3"
+			, "4"
+		];
+		expect(result).to.deep.equal(expected);
+	});
+
 	it('should allow deleting header', function() {
 		url = base + '/cookie';
 		return fetch(url).then(function(res) {