AngularJS- Dynamic Loading of script files using L

问题:

Right now in my index.html page I have links to two CDN files one being a JS and the other a CSS file.

i.e. in the the bottom of my body

https://somedomain.com/files/js/js.min.js

and in the head

https://somedomain.com/files/css/css.min.css

But right now they aren't needed on my homepage but just in one particular route. So I was looking into how I can lazy load these CDN resources when that routes gets hit i.e. /profile and only then ?

These aren't installed via bower or npm but just loaded via CDN url for example jquery. How in Angular 1 and Webpack can I lazy load that based on a route ?

回答1:

Here you go.. It is made possible using oclazyload. Have a look at below code. A plunker linked below

I have a module Called myApp as below

angular.module('myApp', ['ui.router','oc.lazyLoad'])
    .config(function ($stateProvider, $locationProvider, $ocLazyLoadProvider) {
            $stateProvider
                .state("home", {
                    url: "/home",
                    templateUrl: "Home.html",
                    controller: 'homeCtrl',
                    resolve: { 
                        loadMyCtrl: ['$ocLazyLoad', function ($ocLazyLoad) {
                            return $ocLazyLoad.load('homeCtrl.js');
                        }]
                    }
                })
            .state("profile", {
                url:"/profile",
                templateUrl: "profile.html",
                 resolve: {
                      loadMyCtrl: ['$ocLazyLoad', function ($ocLazyLoad) {
                      return $ocLazyLoad.load('someModule.js');
                        }]
                    }
            })

    });

I have another module called someApp as below

(function () {
var mynewapp=angular.module('someApp',['myApp']);

mynewapp.config(function(){

  //your code to route from here! 

});
      mynewapp.controller("profileCtrl", function ($scope) {

            console.log("reached profile controller");
        });

})();

I have a Live Plunker for your demo here

回答2:

I have this JStaticLoader repo, to ease me loading static files whenever I need them. Though, it's not angularized, but you can still use it in your app as a directive, direct call it from your controller or even in the $rootScope to load your desired js.

JStaticLoader uses pure js and require no dependencies. It uses XMLHttpRequest to load the static files.

As an example use in your app.js (on $routeChangeStart or $stateChangeStart)

myApp
.run(['$rootScope', '$http', function ($rootScope, $http) {
    var scriptExists = function (scriptId) {
        if (document.getElementById(scriptId)) {
            return true;
        }

        return false;
    };

    var addLazyScript = function (scriptId, url) {
        if (scriptExists(scriptId)) return;

        var js = document.createElement('script'),
            els = document.getElementsByTagName('script')[0];

        js.id = scriptId;
        js.src = url;
        js.type = "text/javascript";

        els.parentNode.insertBefore(js, els);
    };

    $rootScope.$on('$routeChangeStart', function (e, current) {
        if (current.controller === 'MainCtrl') {
            var pathUrls = ["https://cdnjs.cloudflare.com/ajax/libs/materialize/0.97.8/js/materialize.js"],
                scriptId = 'lazyScript1';

            if (scriptExists(scriptId)) return;

            JStaticLoader(pathUrls, { files: ['js'] }, function (vals, totalTime) {
                /* Success */
                for (var i = 0; i < vals.length; i++) {
                    var path = vals[i];
                    addLazyScript(scriptId, path);
                }
            }, function (error, totalTime) {
                /* Error */
                console.warn(error, totalTime);
            });
        }
    });
}]);

On the sample above, I get a js file by using xhr, and append it as a script in my document once it's finished. The script will then be loaded from your browser's cache.

回答3:

Strictly talking about the Webpack -

Webpack is just a module bundler and not a javascript loader.Since it packages files only from the local storage and doesn't load the files from the web(except its own chunks).ALthough other modules may be included into the webpack which may do the same process.

I will demonstrate only some of the modules which you can try,as there are many such defined on the web.

Therefore a better way to lazy load the cdn from the another domain would be using the javascript loader - script.js

It can be loaded in the following way -

var $script = require("script.js");
 $script = ("https://somedomain.com/files/js/js.min.js or https://somedomain.com/files/css/css.min.css",function(){
 //.... is ready now
});

This is possible because the script-loader just evaluates the javascript in the global context.

References here

Concerning about the issue of lazy loading the cdn into the angular app

The following library Lab JS is made specifically for this purpose. It becomes very simple to load and bloack the javascript using this library.

Here is an example to demonstrate

<script src="LAB.js"></script>
  <script>
    $LAB
     .script("/local/init.js").wait(function(){
       waitfunction();
     });
  <script>

OR

You can use the require.js

Here is an example to load the jquery

require.config({
    paths: {
        "jquery": "https://ajax.googleapis.com/ajax/libs/jquery/1.8.1/jquery.min"
    },
    waitSeconds: 40
  });

You should also consider the following paragraph from this article.

Loading third party scripts async is key for having high performance web pages, but those scripts still block onload. Take the time to analyze your web performance data and understand if and how those not-so-important content/widgets/ads/tracking codes impact page load times.