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394 lines
14 KiB
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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0//EN" "https://www.w3.org/TR/REC-html40/strict.dtd">
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<html>
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<head>
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<META http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
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<base target="_blank">
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<link rel="stylesheet" type="text/css" href="styleguide.css">
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<script src="https://google-code-prettify.googlecode.com/svn/loader/run_prettify.js"></script>
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<script language="javascript" src="/eng/doc/devguide/include/styleguide.js"></script>
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<title>Google's AngularJS Style Guide</title>
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<style type="text/css"><!--
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th { background-color: #ddd; }
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//--></style>
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</head>
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<body onload="prettyPrint();initStyleGuide();">
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<h1 class="external">An AngularJS Style Guide for Closure Users at Google</h1>
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<p class="external">This is the external version of a document that was primarily written for Google
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engineers. It describes a recommended style for AngularJS apps that use Closure, as used
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internally at Google. Members of the broader AngularJS community should feel free to apply
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(or not apply) these recommendations, as relevant to their own use cases.</p>
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<p class="external">This document describes style for AngularJS apps in google3. This guide
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supplements and extends the <a href="https://google.github.io/styleguide/jsguide.html">
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Google JavaScript Style Guide</a>.
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</p>
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<p><b>Style Note</b>: Examples on the AngularJS external webpage, and many external apps, are
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written in a style that freely uses closures, favors functional inheritance, and does not often use
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<a class="external"
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href="https://github.com/google/closure-compiler/wiki/Types-in-the-Closure-Type-System">
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JavaScript types</a>. Google follows a more rigorous Javascript style to support JSCompiler
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optimizations and large code bases - see the javascript-style mailing list.
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This is not an Angular-specific issue, and is not discussed further in this style guide.
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(But if you want further reading:
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<a href="http://martinfowler.com/bliki/Lambda.html">Martin Fowler on closures</a>,
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<a href="http://jibbering.com/faq/notes/closures/">much longer description</a>, appendix A of the
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<a href="https://books.google.com/books/about/Closure_The_Definitive_Guide.html?id=p7uyWPcVGZsC">
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closure book</a> has a good description of inheritance patterns and why it prefers
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pseudoclassical,
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<a href="https://books.google.com/books/about/JavaScript.html?id=PXa2bby0oQ0C">
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Javascript, the Good Parts</a> as a counter.)</p>
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<h5>1 Angular Language Rules</h5>
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<ul>
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<li> <a target="_self" href="#googprovide">Manage dependencies with Closure's goog.require and
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goog.provide</a>
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<li> <a target="_self" href="#modules"> Modules</a>
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<li> <a target="_self" href="#moduledeps"> Modules should reference other modules using the
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"name" property</a>
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<li> <a target="_self" href="#externs">Use the provided Angular externs file</a>
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<li> <a target="_self" href="#compilerflags">JSCompiler Flags</a>
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<li> <a target="_self" href="#controllers">Controllers and Scopes</a>
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<li> <a target="_self" href="#directives">Directives</a>
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<li> <a target="_self" href="#services">Services</a>
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</ul>
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<h5>2 Angular Style Rules</h5>
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<ul>
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<li><a target="_self" href="#dollarsign">Reserve $ for Angular properties and services
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</a>
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<li><a target="_self" href="#customelements">Custom elements.</a>
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</ul>
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<h5>3 Angular Tips, Tricks, and Best Practices</h5>
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<ul>
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<li><a target="_self" href="#testing">Testing</a>
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<li><a target="_self" href="#appstructure">Consider using the Best Practices for App Structure</a>
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<li><a target="_self" href="#scopeinheritance">Be aware of how scope inheritance works</a>
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<li><a target="_self" href="#nginject">Use @ngInject for easy dependency injection compilation</a>
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</ul>
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<h5><a target="_self" href="#bestpractices">4 Best practices links and docs</a></h5>
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<h2>1 Angular Language Rules</h2>
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<h3 id="googprovide">Manage dependencies with Closure's goog.require and goog.provide</h3>
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<p>Choose a namespace for your project, and use goog.provide and goog.require.</p>
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<pre class="prettyprint lang-js">
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goog.provide('hello.about.AboutCtrl');
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goog.provide('hello.versions.Versions');
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</pre>
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<p><b>Why?</b>
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Google BUILD rules integrate nicely with closure provide/require.</p>
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<h3 id="modules">Modules</h3>
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<p>Your main application module should be in your root client directory. A module should never be
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altered other than the one where it is defined.</p>
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<p>Modules may either be defined in the same file as their components (this works well for a module
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that contains exactly one service) or in a separate file for wiring pieces together.</p>
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<p><b>Why?</b>
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A module should be consistent for anyone that wants to include it as a reusable component.
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If a module can mean different things depending on which files are included, it is not consistent.
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</p>
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<h3 id="moduledeps">
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Modules should reference other modules using the Angular Module's "name" property
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</h3>
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<p>For example:</p>
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<pre class="prettyprint lang-js">
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// file submodulea.js:
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goog.provide('my.submoduleA');
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my.submoduleA = angular.module('my.submoduleA', []);
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// ...
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// file app.js
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goog.require('my.submoduleA');
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Yes: my.application.module = angular.module('hello', [my.submoduleA.name]);
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<font color="red">
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No: my.application.module = angular.module('hello', ['my.submoduleA']);
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</font></pre>
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<p><b>Why?</b>
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Using a property of my.submoduleA prevents Closure presubmit failures complaining that the file is
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required but never used. Using the .name property avoids duplicating strings.</p>
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<h3 id="externs">Use a common externs file</h3>
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<p>This maximally allows the JS compiler to enforce type safety in the presence of externally
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provided types from Angular, and means you don't have to worry about Angular vars being obfuscated
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in a confusing way. </p>
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<p>Note to readers outside Google: the current externs file is located in an internal-to-Google
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directory, but an example can be found on github <a href="https://github.com/angular/angular.js/pull/4722">
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here</a>.</p>
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<h3 id="compilerflags">JSCompiler Flags</h3>
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<p><b>Reminder</b>: According to the JS style guide, customer facing code must be compiled.</p>
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<p><b>Recommended</b>: Use the JSCompiler (the closure compiler that works with js_binary by
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default) and ANGULAR_COMPILER_FLAGS_FULL from //javascript/angular/build_defs/build_defs for
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your base flags.
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</p>
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<p>Note - if you are using @export for methods, you will need to add the compiler flag</p>
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<pre>
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"--generate_exports",
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</pre>
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<p>If you are using @export for properties, you will need to add the flags:</p>
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<pre>
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"--generate_exports",
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"--remove_unused_prototype_props_in_externs=false",
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"--export_local_property_definitions",
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</pre>
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<h3 id="controllers">Controllers and Scopes</h3>
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<p>Controllers are classes. Methods should be defined on MyCtrl.prototype.</p>
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<p>Google Angular applications should use the <b>'controller as'</b> style to export the controller
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onto the scope. This is fully implemented in Angular 1.2 and can be mimicked in pre-Angular 1.2
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builds.
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</p>
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<p>Pre Angular 1.2, this looks like:</p>
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<pre class="prettyprint lang-js">
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/**
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* Home controller.
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*
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* @param {!angular.Scope} $scope
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* @constructor
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* @ngInject
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* @export
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*/
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hello.mainpage.HomeCtrl = function($scope) {
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/** @export */
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$scope.homeCtrl = this; // This is a bridge until Angular 1.2 controller-as
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/**
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* @type {string}
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* @export
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*/
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this.myColor = 'blue';
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};
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/**
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* @param {number} a
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* @param {number} b
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* @export
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*/
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hello.mainpage.HomeCtrl.prototype.add = function(a, b) {
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return a + b;
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};
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</pre>
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<p>And the template:</p>
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<pre>
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<div ng-controller="hello.mainpage.HomeCtrl"/>
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<span ng-class="homeCtrl.myColor">I'm in a color!</span>
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<span>{{homeCtrl.add(5, 6)}}</span>
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</div>
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</pre>
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<p>After Angular 1.2, this looks like:</p>
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<pre class="prettyprint lang-js">
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/**
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* Home controller.
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*
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* @constructor
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* @ngInject
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* @export
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*/
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hello.mainpage.HomeCtrl = function() {
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/**
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* @type {string}
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* @export
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*/
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this.myColor = 'blue';
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};
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/**
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* @param {number} a
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* @param {number} b
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* @export
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*/
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hello.mainpage.HomeCtrl.prototype.add = function(a, b) {
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return a + b;
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};
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</pre>
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<p>If you are compiling with property renaming, expose properties and methods using the @export
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annotation. Remember to @export the constructor as well.</p>
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<p>And in the template:</p>
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<pre>
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<div ng-controller="hello.mainpage.HomeCtrl as homeCtrl"/>
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<span ng-class="homeCtrl.myColor">I'm in a color!</span>
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<span>{{homeCtrl.add(5, 6)}}</span>
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</div>
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</pre>
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<p><b>Why?</b>
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Putting methods and properties directly onto the controller, instead of building up a scope
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object, fits better with the Google Closure class style. Additionally, using 'controller as'
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makes it obvious which controller you are accessing when multiple controllers apply to an element.
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Since there is always a '.' in the bindings, you don't have to worry about prototypal inheritance
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masking primitives.</p>
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<h3 id="directives">Directives</h3>
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<p>All DOM manipulation should be done inside directives. Directives should be kept small and use
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composition. Files defining directives should goog.provide a static function which returns the
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directive definition object.</p>
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<pre class="prettyprint lang-js">
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goog.provide('hello.pane.paneDirective');
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/**
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* Description and usage
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* @return {angular.Directive} Directive definition object.
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*/
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hello.pane.paneDirective = function() {
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// ...
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};
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</pre>
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<p><b>Exception</b>: DOM manipulation may occur in services for DOM elements disconnected from the
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rest of the view, e.g. dialogs or keyboard shortcuts.</p>
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<h3 id="services">Services</h3>
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<p>Services registered on the module with <code>module.service</code> are classes.
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Use <code>module.service</code> instead of <code>module.provider</code> or
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<code>module.factory</code> unless you need to do initialization beyond just creating a
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new instance of the class.</p>
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<pre class="prettyprint lang-js">
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/**
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* @param {!angular.$http} $http The Angular http service.
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* @constructor
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*/
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hello.request.Request = function($http) {
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/** @type {!angular.$http} */
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this.http_ = $http;
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};
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hello.request.Request.prototype.get = function() {/*...*/};
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</pre>
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<p>In the module:</p>
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<pre class="prettyprint lang-js">
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module.service('request', hello.request.Request);
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</pre>
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<h2>2 Angular Style Rules</h2>
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<h3 id="dollarsign">Reserve $ for Angular properties and services</h3>
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<p>Do not use $ to prepend your own object properties and service identifiers. Consider this style
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of naming reserved by AngularJS and jQuery.</p>
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<p>Yes:</p>
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<pre class="prettyprint lang-js">
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$scope.myModel = { value: 'foo' }
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myModule.service('myService', function() { /*...*/ });
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var MyCtrl = function($http) {this.http_ = $http;};
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</pre>
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<p><font color="red">No:</font></p>
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<pre class="prettyprint">
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$scope.$myModel = { value: 'foo' } // BAD
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$scope.myModel = { $value: 'foo' } // BAD
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myModule.service('$myService', function() { ... }); // BAD
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var MyCtrl = function($http) {this.$http_ = $http;}; // BAD
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</pre>
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<p><b>Why?</b>
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It's useful to distinguish between Angular / jQuery builtins and things you add yourself.
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In addition, $ is not an acceptable character for variables names in the JS style guide.
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</p>
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<h3 id="customelements">Custom elements</h3>
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<p>For custom elements (e.g. <code><ng-include src="template"></ng-include></code>), IE8
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requires special support (html5shiv-like hacks) to enable css styling. Be aware of this
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restriction in apps targeting old versions of IE.</p>
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<h2>3 Angular Tips, Tricks, and Best Practices</h2>
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<p>These are not strict style guide rules, but are placed here as reference for folks getting
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started with Angular at Google.</p>
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<h3 id="testing">Testing</h3>
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<p>Angular is designed for test-driven development.</p>
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<p>The recommended unit testing setup is Jasmine + Karma (though you could use closure tests
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or js_test)</p>
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<p>Angular provides easy adapters to load modules and use the injector in Jasmine tests.
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<ul>
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<li><a href = "https://docs.angularjs.org/api/angular.mock.module">module</a>
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<li><a href="https://docs.angularjs.org/api/angular.mock.inject">inject</a>
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</ul>
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</p>
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<h3 id="appstructure">Consider using the Best Practices for App Structure</h3>
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<p>
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This <a href="https://docs.google.com/document/d/1XXMvReO8-Awi1EZXAXS4PzDzdNvV6pGcuaF4Q9821Es/pub">directory structure doc</a> describes how to structure your application with controllers in
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nested subdirectories and all components (e.g. services and directives) in a 'components' dir.
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</p>
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<h3 id="scopeinheritance">Be aware of how scope inheritance works</h3>
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<p>See <a href="https://github.com/angular/angular.js/wiki/Understanding-Scopes#wiki-JSproto">
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The Nuances of Scope Prototypal Inheritance</a></p>
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<h3 id="nginject">Use @ngInject for easy dependency injection compilation</h3>
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<p>This removes the need to add <code>myCtrl['$inject'] = ...</code> to prevent minification from
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messing up Angular's dependency injection.</p>
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<p>Usage:</p>
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<pre class="prettyprint lang-js">
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/**
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* My controller.
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* @param {!angular.$http} $http
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* @param {!my.app.myService} myService
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* @constructor
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* @export
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* @ngInject
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*/
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my.app.MyCtrl = function($http, myService) {
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//...
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};
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</pre>
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<h2 id="bestpractices">4 Best practices links and docs</h2>
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<ul>
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<li><a href="https://github.com/angular/angular.js/wiki/Best-Practices">
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Best Practices</a> from Angular on GitHub</li>
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<li><a href="https://www.youtube.com/watch?v=ZhfUv0spHCY">
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Meetup video</a> (not Google specific)</li>
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</ul>
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<address>
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Last modified Feb 07 2013
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</address>
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</body>
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<html>
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