How to dynamically load js files as needed

JavaScript is nothing more than introducing the script tag to the page, but when the project grows

JavaScript is nothing more than introducing the script tag to the page. But when the project grows, N JavaScript codes are introduced to a single page. merging a single file reduces the number of requests, however, the requested file volume is large. At this time, the best practice is to introduce components js and style dynamically as needed. After the file load is complete, call callback to run js. The code is still very simple.

1. Check whether the file load is complete. The loading status of ie is onreadystatechange, and the others are onload and onerror.

if(isie){Res.onreadystatechange = function(){if(Res.readyState == 'complete' || Res.readyState == 'loaded'){Res.onreadystatechange = null;      callback();       _self.loadedUi[modelName] = true;}}}else{Res.onload = function(){Res.onload = null;callback();_self.loadedUi[modelName] = true;}Res.onerror = function(){throw new Error('res error:' + modelName+'.js');}}

2. It is recommended that the names of all components be consistent, and callback calls are convenient. You can also add parameters as needed, such as requires, dependent on those files; style, true | false, whether to load the style, and so on.

3. You can also remove the script, style tag, and delete components.

(Function (window, undefined) {if (! Window. ui) {window. ui ={};}// dynamically load the js window of the ui. bus = {config: {version: window. config. version, cssPath: window. config. resServer + '/css/v3/Ui', jsPath: window. config. resServer + '/js/v2/Ui'}, loadedUi: {}, readyStateChange: function () {var ua = navigator. userAgent. toLowerCase (); return ua. indexOf ('msi')> = 0;}, loadRes: function (modelName, prames, callback) {var _ self = this; var Res = Document. createElement (prames. tagName); for (var k in prames) {if (k! = 'Tagname') {Res. setAttribute (k, prames [k], 0) ;}} document. getElementsByTagName ('head') [0]. appendChild (Res); if (this. readyStateChange () {Res. onreadystatechange = function () {if (Res. readyState = 'complete' | Res. readyState = 'loaded') {Res. onreadystatechange = null; callback (); _ self. loadedUi [modelName] = true ;}} else {Res. onload = function () {Res. onload = null; callback (); _ self. loadedUi [mo DelName] = true;} Res. onerror = function () {throw new Error ('res error: '+ modelName + '. js') ;}}, removeUi: function (modelName) {if (! ModelName) {return true}; this. loadedUi [modelName] = false; var head = document. getElementsByTagName ('head') [0]; var model_js = document. getElementById ('J _ model _ '+ modelName +' _ js'); var model_css = document. getElementById ('J _ model _ '+ modelName +' _ css '); if (model_js & model_css) {delete window. ui [modelName]; head. removeChild (model_js); head. removeChild (model_css); return true;} else {return false ;}}, LoadUi: function (modelName, callback, setting) {if (! ModelName) {return true}; callback = callback | function () {}; if (this. loadedUi [modelName] = true) {callback (); return true} var deafult_setting = {style: true, js: true, requires: []} for (var key in setting) {deafult_setting [key] = setting [key];} deafult_setting ['style'] = true & this. loadRes (modelName, {id: 'J _ model _ '+ modelName +' _ css ', name: modelName, tagName: 'link', type: 'TE Xt/css ', rel: 'stylesheet', href: this.config.css Path + '/' + modelName + '.css? V = '+ this. config. version}); deafult_setting ['js'] === true & this. loadRes (modelName, {id: 'J _ model _ '+ modelName +' _ js', name: modelName, tagName: 'script', type: 'text/javascript ', src: this. config. jsPath + '/' + modelName + '. js? V = '+ this. config. version}, callback); if (deafult_setting.requires.length> 0) {for (var I = 0, len = deafult_setting.requires.length; I <len; I ++) {this. loadUi (deafult_setting.requires [I]) ;}}}) (window)

Usage:

// load comment for feed    window.bus.loadUi('new_comment_feed', function(){        window.ui.new_comment_feed($("#J_newsList"));    },{        style : false,        requires:['emoticon','addFriend']    });    // load new yy ui    window.bus.loadUi('yy', function(){        window.ui.yy(options);    },{        style:false,        requires:['emoticon']    });    // load photoLightbox    window.bus.loadUi('photoLightbox', function(){        window.ui.photoLightbox(options.urlAjaxGetFriendPhoto, options.urlCommentOtherPhoto,$("#J_newsList"),options.myUid,options.myName);    });

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