Writing your First Angular 2 Web Application 6
Angular’s Dependencies
You don’t strictly need to understand these dependencies in-depth in order to use Angular
2, but you do need to include them. Feel free to skip this section if you’re not that interested
in the dependencies, but make sure you copy and paste these script tags.
To run Angular 2, we depend on these four libraries:
• es6-shim
• zone.js
• reflect-metadata
• SystemJS
To include them, add the following inside your <head>
1 <script src="node_modules/es6-shim/es6-shim.js"></script>
2 <script src="node_modules/zone.js/dist/zone.js"></script>
3 <script src="node_modules/reflect-metadata/Reflect.js"></script>
4 <script src="node_modules/systemjs/dist/system.src.js"></script>
Notice that we’re loading these .js files directly from a directory called node_-
modules. The node_modules directory will be created when you run npm install. If
you don’t have a node_modules directory, make sure your shell was “in” the directory
angular2-reddit-base (e.g. by using cd angular2-reddit-base) when you typed npm
install.
ES6 Shim
ES6 provides shims so that legacy JavaScript engines behave as closely as possible to ECMAScript 6.
This shim isn’t strictly needed for newer versions of Safari, Chrome, etc. but it is required for older
versions of IE.
What’s a shim? Perhaps you’ve heard about shims or polyfills and you’re not sure what
they are. A shim is code that helps adapt between cross browsers to a standardized behavior.
For instance, check out this ES6 Compatibility Table⁹. Not every browser is completely
compatible with every feature. By using different shims we’re able to get standardized
behavior across different browsers (and environments).
See also: What is the difference between a shim and a polyfill?¹⁰
⁹https://kangax.github.io/compat-table/es6/
¹⁰http://www.2ality.com/2011/12/shim-vs-polyfill.html
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