JavaScript IF/ELSE 调用另一个 JS 脚本？
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JavaScript IF/ELSE to call another JS Script?
提问by Shafique
I need to call one of two JavaScripts depending on a condition, like so:
我需要根据条件调用两个 JavaScript 之一，如下所示：
<script type="text/javascript">
if(b_condition)
<script type="text/javascript" src="http://script1.js"></script>
else
<script type="text/javascript" src="http://script2.js"></script>
</script>
But this doesnt work. Any ideas how to call another JavaScript call in an If/Else block?
但这不起作用。任何想法如何在 If/Else 块中调用另一个 JavaScript 调用？
回答by Ryan McGrath
What the hell? Why on earth is everyone here advocating document.write()? Fairly certain we've moved beyond this as standard practice by this point; document.write isn't even valid if you're in an XHTML setting.
我勒个去？为什么这里的每个人都在提倡 document.write()？相当肯定，我们已经超越了这一点作为标准做法；如果您处于 XHTML 设置中， document.write 甚至无效。
The best way to do this would be something like the following (also here, for better highlighting/parsing: https://gist.github.com/767131):
最好的方法是这样的（也在这里，为了更好地突出显示/解析：https: //gist.github.com/767131）：
/* Since script loading is dynamic/async, we take
a callback function with our loadScript call
that executes once the script is done downloading/parsing
on the page.
*/
var loadScript = function(src, callbackfn) {
var newScript = document.createElement("script");
newScript.type = "text/javascript";
newScript.setAttribute("async", "true");
newScript.setAttribute("src", src);
if(newScript.readyState) {
newScript.onreadystatechange = function() {
if(/loaded|complete/.test(newScript.readyState)) callbackfn();
}
} else {
newScript.addEventListener("load", callbackfn, false);
}
document.documentElement.firstChild.appendChild(newScript);
}
if(a) {
loadScript("lulz.js", function() { ... });
} else {
loadScript("other_lulz.js", function() { ... });
}
If you have jQuery or a similar library on the page, you can Hyman out my loadScript function and insert their appropriate function (ala $.getScript, etc).
如果页面上有 jQuery 或类似的库，您可以取出我的 loadScript 函数并插入相应的函数（ala $.getScript 等）。
回答by spinon
You could do something like this:
你可以这样做：
var file=document.createElement('script')
file.setAttribute("type","text/javascript")
file.setAttribute("src", "script1.js")
Forgot to add that you need to then append this into an element on the page:
忘了补充一点，您需要将其附加到页面上的元素中：
document.getElementsByTagName("head")[0].appendChild(file)
回答by Shafique
I used this and it works well:
我用过这个，效果很好：
<script type="text/javascript">
if(b_condition)
document.write('<scri'+'pt src="http://script1.js"></'+'script>');
else
document.write('<scri'+'pt src="http://scripts2.js"></'+'script>');
</script>
I see that document.write is not the best practice to use though, but it works. Any ideas better than this? I don't want to write so much code for something so simple.
我看到 document.write 不是使用的最佳实践，但它有效。还有比这更好的想法吗？我不想为这么简单的事情写这么多代码。
回答by pruthwiraj.kadam
<script type="text/javascript">
if(condition==true)
{
var src = "js/testing_true.js";
var newScript = document.createElement("script");
newScript.type = "text/javascript";
newScript.setAttribute("async", "true");
newScript.setAttribute("src", src);
document.body.appendChild(newScript);
}else
{
var src = "js/testing_false.js";
var newScript = document.createElement("script");
newScript.type = "text/javascript";
newScript.setAttribute("async", "true");
newScript.setAttribute("src", src);
document.body.appendChild(newScript);
}
</script>
回答by Felix Kling
If the scripts are not huge and/or there is no other reason why not both should be loaded, I would do something like:
如果脚本不是很大和/或没有其他原因不应该加载两者，我会这样做：
<script type="text/javascript" src="http://script1+2.js"></script>
<script type="text/javascript">
if(b_condition) {
functionA();
}
else {
functionB();
}
</script>
回答by moribvndvs
You need to either emit the desired scriptblock in your condition, or create the scripttag using the DOM and insert it. http://ajaxpatterns.org/On-Demand_Javascript
您需要script在您的条件中发出所需的块，或者script使用 DOM创建标签并插入它。http://ajaxpatterns.org/On-Demand_Javascript
回答by Arthur Neves
Those files script1.js and script2.js are your, or are u including them from another domain?
这些文件 script1.js 和 script2.js 是你的，还是你从另一个域中包含它们？
because if they are yours your can include both, and depends of your condition you can call functions inside the files..
因为如果它们是你的，你可以同时包含两者，并且取决于你的条件，你可以在文件中调用函数..
回答by Wolph
This is usually a bad idea so I recommend that you tell us what you actually need to do so we can find a better solution for you. In general you would like to combine and minify all javascript needed on the page so the user only has to load it once.
这通常是一个坏主意，因此我建议您告诉我们您实际需要做什么，以便我们为您找到更好的解决方案。通常，您希望合并和缩小页面上所需的所有 javascript，以便用户只需加载一次。
If there is no other way than you can do it like this:
如果没有其他方法，您可以这样做：
<script type="text/javascript">
var script = document.createElement('script');
if((b_condition){
script.src = 'script1.js';
}else{
script.src = 'script1.js';
}
document.body.appendChild(script);
</script>
回答by Soccerwidow
<?php if (a_condition) {?>
put html code here or script or whatever you like
<?php } elseif(b_condition) {?>
put any other code here
<?php } else {?>
put even more code
<?php } ?>
回答by alexwen
<script type="text/javascript">
if(b_condition)
document.write('<script type="text/javascript" src="http://script1.js"></script>');
else
document.write('<script type="text/javascript" src="http://script2.js"></script>');
</script>
