带有 eval 的 Javascript AJAX 包含文件
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Javascript AJAX include file witth eval
提问by Tom
Suppose I have
假设我有
1) a HTML document.
1) 一个 HTML 文档。
2) This HTML document loads Javascript file "code.js" like this:
2) 这个 HTML 文件像这样加载 Javascript 文件“code.js”：
<script src="code.js">
3) User clicks button which runs "fetchdata" function in "code.js",
3) 用户点击在“code.js”中运行“fetchdata”函数的按钮，
4) "fetchdata" function looks like this:
4) “fetchdata”函数如下所示：
var xmlhttp = new XMLHttpRequest();
xmlhttp.onreadystatechange = function() {
if (xmlhttp.readyState==4) {
myjsdata = xmlhttp.responseText;
}
}
xmlhttp.open("GET", 'http://www.example.com/data.js', false);
xmlhttp.send(null);
...
...
Now how do I do the following successfully:
现在我如何成功执行以下操作：
I want to insert/eval my Javascript in a way, so all functions in "code.js" including "fetchdata" and functions defined above/below can access the data (structures, declarations, pre-calculated data values etc.) in "data.js".
我想以某种方式插入/评估我的 Javascript，因此“code.js”中的所有函数（包括“fetchdata”和上面/下面定义的函数）都可以访问“中的数据（结构、声明、预先计算的数据值等）”数据.js”。
(If this was possible, it would be idea since I could wait loading the actual JS data file until the user explicitly requests it.)
（如果这是可能的，那将是个好主意，因为我可以等待加载实际的 JS 数据文件，直到用户明确请求它。）
回答by mowwwalker
jQuery always has something for everything:
jQuery 总能满足一切需求：
http://api.jquery.com/jQuery.getScript/
http://api.jquery.com/jQuery.getScript/
Loads a javascript file from url and executes it in the global context.
从 url 加载一个 javascript 文件并在全局上下文中执行它。
edit:Oops, didn't see that you weren't using jQuery. Everyone is always using jQuery...
编辑：哎呀，没看到你没有使用 jQuery。每个人都一直在使用 jQuery...
Just do:
做就是了：
var scrpt = document.createElement('script');
scrpt.src='http://www.example.com/data.js';
document.head.appendChild(scrpt);
回答by Joseph
回答by Jeffrey Sweeney
This depends on a lot of factors, but in most cases, you will want to load all of your code/html/css in one sitting. It takes fewer requests, and thus boast a higher perceived performance benefit. Unless your code file is over several Megabytes big, loading it when a user requests it is unnecessary.
这取决于很多因素，但在大多数情况下，您会希望一次性加载所有代码/html/css。它需要更少的请求，因此拥有更高的感知性能优势。除非您的代码文件超过几兆字节，否则在用户请求时加载它是不必要的。
In addition to all of this, modifying innerHTMLand running scripts via evalcan be very cumbersome and risky (respectively). Many online references will back this point. Don't assume that, just because a library is doing something like this, it is safe to perform.
除此之外，修改innerHTML和运行脚本通过eval可能非常麻烦和风险（分别）。许多在线参考资料都会支持这一点。不要认为，仅仅因为图书馆正在做这样的事情，就可以安全地执行。
That said, it is entirely possible to load external js files and execute them. One way is to stick all of the code into a newly created script tag. You can also just try running the code in an evalfunction call (though it isn't recommended).
也就是说，完全可以加载外部 js 文件并执行它们。一种方法是将所有代码粘贴到新创建的脚本标签中。您也可以尝试在eval函数调用中运行代码（尽管不推荐这样做）。
address = "testscript.js";
var req = (window.XMLHttpRequest)?new XMLHttpRequest():new ActiveXObject("Microsoft.XMLHTTP");
if(req == null) {
console.log("Error: XMLHttpRequest failed to initiate.");
}
req.onload = function() {
try {
eval(req.responseText);
} catch(e) {
console.log("There was an error in the script file.");
}
}
try {
req.open("GET", address, true);
req.send(null);
} catch(e) {
console.log("Error retrieving data httpReq. Some browsers only accept cross-domain request with HTTP.");
}
