我有一个动态网页,我需要在另一个javascript文件内导入一个外部JS文件(在IF条件下)。

我试图寻找一个可行的解决办法,但没有成功。

我尝试使用document.createElement()将JS文件加载到DOM,但它也不起作用。显然,Js被加载到DOM中,但在当前Js文件中无法访问。

解决方案在jQuery也将很好


当前回答

我建议使用AMD javascript类文件requirejs

这是一个很好的例子

http://www.sitepoint.com/understanding-requirejs-for-effective-javascript-module-loading/

其他回答

我需要经常这样做,所以我使用这个:

var loadJS = function(url, implementationCode, location){
    //url is URL of external file, implementationCode is the code
    //to be called from the file, location is the location to 
    //insert the <script> element

    var scriptTag = document.createElement('script');
    scriptTag.src = url;

    scriptTag.onload = implementationCode;
    scriptTag.onreadystatechange = implementationCode;

    location.appendChild(scriptTag);
};
var yourCodeToBeCalled = function(){
//your code goes here
}
loadJS('yourcode.js', yourCodeToBeCalled, document.body);

有关更多信息,请参阅本网站如何在另一个JavaScript文件中包含一个JavaScript文件?,这是我的函数思想的来源。

为了编写我的插件,我需要在JS文件中加载外部脚本和样式,所有这些都是预定义的。为了实现这一目标,我做了以下事情:

    this.loadRequiredFiles = function (callback) {
        var scripts = ['xx.js', 'yy.js'];
        var styles = ['zz.css'];
        var filesloaded = 0;
        var filestoload = scripts.length + styles.length;
        for (var i = 0; i < scripts.length; i++) {
            log('Loading script ' + scripts[i]);
            var script = document.createElement('script');
            script.type = 'text/javascript';
            script.src = scripts[i];
            script.onload = function () {
                log('Loaded script');
                log(this);
                filesloaded++;  // (This means increment, i.e. add one)
                finishLoad();
            };
            document.head.appendChild(script);
        }
        for (var i = 0; i < styles.length; i++) {
            log('Loading style ' + styles[i]);
            var style = document.createElement('link');
            style.rel = 'stylesheet';
            style.href = styles[i];
            style.type = 'text/css';
            style.onload = function () {
                log('Loaded style');
                log(this);
                filesloaded++;
                finishLoad();
            };
            document.head.appendChild(style);
        }
        function finishLoad() {
            if (filesloaded === filestoload) {
                callback();
            }
        }
    };

更多上下文中的脚本:

function myPlugin() {

    var opts = {
        verbose: false
    };                          ///< The options required to run this function
    var self = this;            ///< An alias to 'this' in case we're in jQuery                         ///< Constants required for this function to work

    this.getOptions = function() {
        return opts;
    };

    this.setOptions = function(options) {
        for (var x in options) {
            opts[x] = options[x];
        }
    };

    /**
     * @brief Load the required files for this plugin
     * @param {Function} callback A callback function to run when all files have been loaded
     */
    this.loadRequiredFiles = function (callback) {
        var scripts = ['xx.js', 'yy.js'];
        var styles = ['zz.css'];
        var filesloaded = 0;
        var filestoload = scripts.length + styles.length;
        for (var i = 0; i < scripts.length; i++) {
            log('Loading script ' + scripts[i]);
            var script = document.createElement('script');
            script.type = 'text/javascript';
            script.src = scripts[i];
            script.onload = function () {
                log('Loaded script');
                log(this);
                filesloaded++;
                finishLoad();
            };
            document.head.appendChild(script);
        }
        for (var i = 0; i < styles.length; i++) {
            log('Loading style ' + styles[i]);
            var style = document.createElement('link');
            style.rel = 'stylesheet';
            style.href = styles[i];
            style.type = 'text/css';
            style.onload = function () {
                log('Loaded style');
                log(this);
                filesloaded++;
                finishLoad();
            };
            document.head.appendChild(style);
        }
        function finishLoad() {
            if (filesloaded === filestoload) {
                callback();
            }
        }
    };

    /**
     * @brief Enable user-controlled logging within this function
     * @param {String} msg The message to log
     * @param {Boolean} force True to log message even if user has set logging to false
     */
    function log(msg, force) {
        if (opts.verbose || force) {
            console.log(msg);
        }
    }

    /**
     * @brief Initialise this function
     */
    this.init = function() {
        self.loadRequiredFiles(self.afterLoadRequiredFiles);
    };

    this.afterLoadRequiredFiles = function () {
        // Do stuff
    };

}

下面是一个动态加载javascript和CSS文件的小库:

https://github.com/todotresde/javascript-loader

我想按顺序和动态加载css和js文件是有用的。

支持扩展来加载任何你想要的库,而不仅仅是主文件,你可以用它来加载自定义文件。

例如:

<html>
<head>
    <script src="//ajax.googleapis.com/ajax/libs/jquery/1.10.2/jquery.min.js"></script>
    <script src="scripts/javascript-loader.js" type="text/javascript" charset="utf-8" ></script>    
    <script type="text/javascript">
        $(function() {

            registerLib("threejs", test);

            function test(){
                console.log(THREE);
            }

            registerLib("tinymce", draw);

            function draw(){
                tinymce.init({selector:'textarea'});
            }

        }); 
    </script>
</head>
<body>
    <textarea>Your content here.</textarea>
</body>

我猜在你的dom解决方案中,你做了如下的事情:

var script = document.createElement('script');
script.src = something;
//do stuff with the script

首先,这是行不通的,因为脚本没有被添加到文档树中,所以它不会被加载。而且,即使你这样做了,当另一个脚本正在加载时,javascript的执行仍在继续,所以它的内容在脚本完全加载之前是不可用的。

您可以侦听脚本的load事件,并按照您的意愿对结果进行处理。所以:

var script = document.createElement('script');
script.onload = function () {
    //do stuff with the script
};
script.src = something;

document.head.appendChild(script); //or something of the likes

jQuery的$.getScript()有时是bug,所以我使用我自己的实现,如:

jQuery.loadScript = function (url, callback) {
    jQuery.ajax({
        url: url,
        dataType: 'script',
        success: callback,
        async: true
    });
}

像这样使用它:

if (typeof someObject == 'undefined') $.loadScript('url_to_someScript.js', function(){
    //Stuff to do after someScript has loaded
});