- Angular CLI understands browsers support range from
- If the application needs to support ES5 browsers and TypeScript target is higher than es5, the CLI automatically makes additional bundles for compatibility.
browserslistis the single source of truth, so
es5BrowserSupportwill be deprecated.
Angular CLI v8 (now in beta.15) ships new feature called “Differential Loading”. It allows us to get free from considering browser compatibility of your application.
The CLI can understand browsers which the app needs to support and can make different bundles for both ES5 browsers and not.
How to use
To enable differential loading, the app must have
browserslist configuration. It can be placed in
browserslist file. This configuration has already been used by autoprefixer process of postcss. Apps created recently by CLI should contain it and you can find it in the project.
Even if you don’t have it now, you can create easily with online demo. Angular CLI can look it up if
browserslist file is placed at the same directory to
Preparation is over! If your tsconfig’s target is out of browser range determined by
browserslist , Angular CLI will separate bundles; one is for original target, and another is for ES5 browsers.
For example, let’s support the latest 2 versions of Chrome and IE 11.
browserslist is the following;
last 2 Chrome versions, IE 11
tsconfig.json is like below.
As you may know, IE11 is an ES5 browser. So without differential loading, this application will throw errors on IE11 because of missing
es2015 features like arrow functions,
class or etc…
With differential loading, Angular CLI understand this problem in advance. The CLI judges whether the app has to support ES5 browsers, and check the current tsconfig’s target can support them. If they are mismatched, all bundles are separated as like
<script> tags for ES5 bundles are placed with
nomodule attribute. It avoids loading ES5 bundles on non-ES5 browsers. As a result, on modern browsers, users will load smaller bundles just that the browser needs. It can improve loading performance.
Yes, Angular CLI v7.3 added a feature like differential loading but it is only for polyfills. It uses
es5BrowserSupport option in
After Angular CLI v8, it will be deprecated because it is not simple to manage supporting browsers in both of
browserslist for CSS and
browserslist as the single source of truth to judge whether the application needs to support ES5 browsers.
- Differential loading has been landed in Angular CLI v8 beta.
- CLI uses
browserslistto judge the application needs to support ES5 browsers.
- If tsconfig doesn’t match that, CLI adds different bundles loaded only by ES5 browsers.
To try the feature, let’s create an application with the following command;
$ npx @angular/cli@next new example-app
$ cd example-app
$ npm run build
Thanks for reading!