在js中加载jQuery，然后执行依赖于它的脚本 [英] Load jQuery in a js, then execute a script that depends on it

问题描述

我有一个独特的问题 -

I have a unique issue -

我正在设计一个创建小部件的Web应用程序，然后用户可以将这些小部件嵌入到他们自己的页面中（主要是博客文章）。我希望他们只需要嵌入一行，所以我只是将该行作为include语句，从我的服务器上取下Javascript。

I am designing a web application that creates widgets that a user can then embed in their own page (blog posts, mostly). I want them to just have to embed one line, so I just had that line be an include statement, to pull a Javascript off my server.

问题是，我正在使用jQuery构建窗口小部件代码，我需要加载jQuery插件，因为我显然不知道我的用户是否会有它。我认为'这应该很简单'....

The problem is, I am building the widget code using jQuery, and I need to load the jQuery plugin, since I obviously don't know whether or not my users will have it available. I thought 'this should be pretty simple'....

function includeJavaScript(jsFile) {
  var script = document.createElement('script');
  script.src = jsFile;
  script.type = 'text/javascript';
  document.getElementsByTagName('head')[0].appendChild(script);
}

includeJavaScript('http://ajax.googleapis.com/ajax/libs/jquery/1.4.2/jquery.min.js');
jQuery();

所以，我将jQuery文件附加到头部，然后尝试运行jQuery函数。麻烦的是，这不起作用！每次运行它时，我都会收到错误，即未定义变量jQuery。我尝试了一些事情。我尝试将jQuery函数放在onLoad触发器中，以便整个页面（包括，可能是jQuery文件）在调用我的脚本之前加载。我尝试将jQuery函数放在一个单独的文件中，并在加载jQuery lib文件后加载它。但我明白我错过了一些简单的东西 - 我是jQuery的新手，所以如果我遗漏了一些明显的东西，我道歉......

So, I am appending the jQuery file to the head, then afterwards, trying to run a jQuery function. Trouble is, this doesn't work! Everytime I run it, I get the error that variable jQuery is not defined. I have tried a few things. I tried putting the jQuery functions in an onLoad trigger, so that the whole page (including, presumably, the jQuery file) would load before it called my script. I tried putting the jQuery function in a seperate file, and loading it after loading the jQuery lib file. But I get the idea I'm missing something simple - I'm new to jQuery, so if I'm missing something obvious, I apologize...

EDIT

好的，我尝试了digitalFresh提供的建议，如下（使用Safari 5，如果有帮助），但我仍然得到同样的错误？

OK,I tried the suggestion offered by digitalFresh, as follows (using Safari 5, if that helps), but I still get the same error?

function test() {
    jQuery()
}

var script = document.createElement("script");
script.type = "text/javascript";
script.src = 'http://ajax.googleapis.com/ajax/libs/jquery/1.4.2/jquery.min.js';
script.onload = test(); //execute
document.body.appendChild(script);

编辑

好的，我最后得到了它可以在Brendan的一个随意的建议下工作，将ITSELF调用一个'onload'处理程序，如下所示：

OK, I FINALLY got it to work, in an offhand suggestion from Brendan, by putting the call ITSELF in an 'onload' handler, like so:

function addLoadEvent(func) { 
      var oldonload = window.onload; 
      if (typeof window.onload != 'function') { 
        window.onload = func; 
      } else { 
        window.onload = function() { 
          if (oldonload) { 
            oldonload(); 
          } 
          func(); 
        } 
    } 
} 
addLoadEvent( function() {
    var script = document.createElement("script");
    script.type = "text/javascript";
    script.src = 'http://ajax.googleapis.com/ajax/libs/jquery/1.4.2/jquery.min.js';
    document.body.appendChild(script);
    jQuery();
});

此时，正如你所看到的，我甚至不需要把它放进' onload' - 它只是有效。虽然我不得不承认，我仍然不明白为什么它有效，这让我感到困扰...

At this point, as you can see, I don't even have to put it in an 'onload' - it just works. Though I have to admit, I still don't understand WHY it works, which bothers me...

推荐答案

你应该先检查以确保他们还没有使用jquery，例如：

You should first check to make sure they do not already use jquery so something like:

if (jQuery) {  
    // jQuery is loaded  
} else {
    // jQuery is not loaded
}

其次，你应该确保在没有冲突模式中使用jQuery而不是使用$运算符，因为它可能被另一个脚本库声明。

Secondly, you should make sure you use jQuery in no conflict mode and do not use the $ operator as it may be claimed by another script library.

然后嵌入，声明这个函数：

Then to embed, declare this function:

function load_script (url)
 {
   var xmlhttp;
   try {
     // Mozilla / Safari / IE7
     xmlhttp = new XMLHttpRequest();
    } catch (e) {
      //Other IE
      xmlhttp = new ActiveXObject("Msxml2.XMLHTTP");
    }
    xmlhttp.open('GET', url, false); x.send('');
    eval(xmlhttp.responseText);
    var s = xmlhttp.responseText.split(/\n/);
    var r = /^function\s*([a-z_]+)/i; 

      for (var i = 0; i < s.length; i++)
      {
          var m = r.exec(s[i]);
          if (m != null)
              window[m[1]] = eval(m[1]);
      }
  } 

然后调用它：

load_script('http://ajax.googleapis.com/ajax/libs/jquery/1.4.2/jquery.min.js');

希望这有帮助。

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