@angular/cli：如何让@angular/cli生成的项目兼容IE9/10/11？

一个恶心的事情是：@angular/cli 生成的项目默认不能很好地支持IE，9/10/11都不行。

好消息是：@angular/cli默认生成了polyfill.ts文件，只要简单几个步骤就可以支持了。

第一步：用@angular/cli创建项目

ng new ie-test
cd ie-test
ng serve

打开你的chrome浏览器，访问http://localhost:4200，很顺利地看到以下界面：

然后，打开IE，很自然地报错了：

仔细看报错信息，你就可以发现，这是因为IE不支持ES6里面给Array扩展的for...of循环导致的。

浏览器对ES6的支持程度，你可以在MDN上查到详细的信息：

第二步：解决问题

打开@angular/cli自动生成的polyfill.ts文件，你可以看到这样的内容：

/**
 * This file includes polyfills needed by Angular and is loaded before the app.
 * You can add your own extra polyfills to this file.
 *
 * This file is divided into 2 sections:
 *   1. Browser polyfills. These are applied before loading ZoneJS and are sorted by browsers.
 *   2. Application imports. Files imported after ZoneJS that should be loaded before your main
 *      file.
 *
 * The current setup is for so-called "evergreen" browsers; the last versions of browsers that
 * automatically update themselves. This includes Safari >= 10, Chrome >= 55 (including Opera),
 * Edge >= 13 on the desktop, and iOS 10 and Chrome on mobile.
 *
 * Learn more in https://angular.io/docs/ts/latest/guide/browser-support.html
 */

/***************************************************************************************************
 * BROWSER POLYFILLS
 */

/** IE9, IE10 and IE11 requires all of the following polyfills. **/
import 'core-js/es6/symbol';
import 'core-js/es6/object';
import 'core-js/es6/function';
import 'core-js/es6/parse-int';
import 'core-js/es6/parse-float';
import 'core-js/es6/number';
import 'core-js/es6/math';
import 'core-js/es6/string';
import 'core-js/es6/date';
import 'core-js/es6/array';
import 'core-js/es6/regexp';
import 'core-js/es6/map';
import 'core-js/es6/weak-map';
import 'core-js/es6/set';

/** IE10 and IE11 requires the following for NgClass support on SVG elements */
import 'classlist.js';  // Run `npm install --save classlist.js`.
/** IE10 and IE11 requires the following for the Reflect API. */
import 'core-js/es6/reflect';


/** Evergreen browsers require these. **/
// Used for reflect-metadata in JIT. If you use AOT (and only Angular decorators), you can remove.
import 'core-js/es7/reflect';


/**
 * Required to support Web Animations `@angular/platform-browser/animations`.
 * Needed for: All but Chrome, Firefox and Opera. http://caniuse.com/#feat=web-animation
 **/
import 'web-animations-js';  // Run `npm install --save web-animations-js`.
/**
 * By default, zone.js will patch all possible macroTask and DomEvents
 * user can disable parts of macroTask/DomEvents patch by setting following flags
 */

 // (window as any).__Zone_disable_requestAnimationFrame = true; // disable patch requestAnimationFrame
 // (window as any).__Zone_disable_on_property = true; // disable patch onProperty such as onclick
 // (window as any).__zone_symbol__BLACK_LISTED_EVENTS = ['scroll', 'mousemove']; // disable patch specified eventNames
 /*
 * in IE/Edge developer tools, the addEventListener will also be wrapped by zone.js
 * with the following flag, it will bypass `zone.js` patch for IE/Edge
 */
// (window as any).__Zone_enable_cross_context_check = true;
/***************************************************************************************************
 * Zone JS is required by default for Angular itself.
 */
import 'zone.js/dist/zone';  // Included with Angular CLI.


/***************************************************************************************************
 * APPLICATION IMPORTS
 */

对于这一坨import在干什么，你仔细看每一行代码后面的注释就知道了。

这里有一个小注意点，有两个依赖需要你手动安装：

npm install --save classlist.js
npm install --save web-animations-js

装完之后重新：

ng serve

然后你就可以在IE里面哈皮地看到这个了：