Writing Conditional Code for Internet Explorer WIT

问题:

I'd like to know if it's possible to write conditional javascript within a javascript file for Internet Explorer.

i.e. something like this...

if (is IE7) {
    do this } else {
    do this instead
});

I know I can load a completely different script for IE using conditional comments in the head, but I only want to change a small piece of code and so loading a completely different sheet would be an 'expensive' way to do that.

回答1:

If you are using jquery you code do this

if ($.browser.msie && $.browser.version == '6.0') {
     //do IE specific code
}

回答2:

When writing Javascript, doing feature detection is always the way to go instead of browser detection. So instead of doing if (IE7) do if (feature).

For example, if you want to know if your browser supports getElementsByClassName(), instead of checking the browser version, you check for the existence of the function ( if (document.getElementsByClassName) ).

Please read this great article:

Object detection on Quirksmode

If you want to know whether the browser that views your page supports certain objects you want to use in your code, you should never EVER use a browser detect. Sure, you know that this–and–that browser will support your code while such–and–so browser won’t. But how about other browsers, obscure browsers?

回答3:

Not within the JavaScript file directly.

A few alternatives would be:

Using a global variable before the script is loaded to check in your JavaScript file. This is a bit of a hybrid approach and could get messy, but it's guaranteed IE detection.

<!--[if IE]>
<script type="text/javascript">
  var is_ie = true;
</script>
<![endif]-->
<script type="text/javascript" src="somefile.js"></script>

Or, a more traditional approach using browser or object detection within the JavaScript file.

回答4:

Conditional compilation is exactly what you are looking for.

<script>
/*@cc_on

  @if (@_jscript_version == 5.7 && window.XMLHttpRequest)
    document.write("You are using IE7");

  @end

@*/
</script>

回答5:

My go-to script for this is PPK's BrowserDetect script. It's lightweight, easily understandable, and doesn't require you to use a library. When it's loaded, you can write code like:

if (BrowserDetect.browser == "Explorer" && BrowserDetect.version >= 6 && BrowserDetect.version <= 8) {
    // IE6-8 code
{

Of course, you should avoid using this at all (reasonable) costs, but there's times where it's cleaner to quarantine IE-specific code away rather than try to hack around IE-specific functions and bugs.

回答6:

Despite the fact that this is an answer to the original question, this is NOT what you should do. So don't do it!

Why not work out which browser you are using and store that in a variable in javascript. Then you can have if statemenets and the like in your javascript. e.g. If I am IE then do this, otherwise do that. You get the idea!

Have you seen this? Browser sniffing

The salient bit:

var is = {
  ff: window.globalStorage,
  ie: document.all && !window.opera,
  ie6: !window.XMLHttpRequest,
  ie7: document.all && window.XMLHttpRequest && !XDomainRequest && !window.opera,
  ie8: document.documentMode==8,
  opera: Boolean(window.opera),
  chrome: Boolean(window.chrome),
  safari: window.getComputedStyle && !window.globalStorage && !window.opera
}

回答7:

If you want to use jquery, it has a built in browser detect.

http://api.jquery.com/jQuery.browser/