Merge pull request #47 from jhnns/fix/illegal-invocation

Fix illegal invocation errors

src/index.js

@@ -1,4 +1,4 @@
-export default typeof fetch=='function' ? fetch : function(url, options) {
+export default typeof fetch=='function' ? fetch.bind() : function(url, options) {
 	options = options || {};
 	return new Promise( (resolve, reject) => {
 		let request = new XMLHttpRequest();

test/index.js

@@ -2,14 +2,31 @@ import fetch from '../src';
 import chai, { expect } from 'chai';
 import { spy, stub } from 'sinon';
 import sinonChai from 'sinon-chai';
-chai.use(sinonChai);
+import { transformFileSync } from 'babel-core';
+import vm from 'vm';
 
+chai.use(sinonChai);
 
 describe('unfetch', () => {
 	it('should be a function', () => {
 		expect(fetch).to.be.a('function');
 	});
 
+	// Prevents illegal invocation errors
+	// See https://github.com/developit/unfetch/issues/46
+	it('should bind the native fetch on window', () => {
+		const filename = require.resolve('../src');
+		const sandbox = {
+			window: {},
+			fetch() { return this },
+			exports: {}
+		};
+
+		vm.runInNewContext(transformFileSync(filename).code, sandbox, filename);
+
+		expect(sandbox.exports.default()).to.equal(sandbox.window);
+	});
+
 	describe('fetch()', () => {
 		it('sanity test', () => {
 			let xhr = {