JQuery select a variable by passing a text string of its name

Not sure what your end target is, but I use the following method a lot when I need one thing to interact with another...

<a href='whatever.html' rel='#targetElem' class='loadable'>
<script>
$(document).ready(function(){
  $('.loadable').live('click',function(){  //when a element with the class of loadable is clicked
    $($(this).attr('rel')).load($(this).attr('href')); //load the contents of it's href URL into the element specified in it's rel attribute
    return(false); // stop processing the link;
 });
});

</script>

I tell the element what the target of the action will be using the rel attribute...

to get at variables try this (window is a javascript built-in array of global variables...)

var i=2;

var test='i';
document.write('got ' + window[test]);

Not sure, but maybe you are looking for eval function.

What you are asking is best done with JavaScript objects, e.g.:

var obj = { test: "xxx" };
for(key in obj) {
    alert(key);  // "test"  
    alert(obj.key); // "xxx"  
}

You can do something like this, though I really don't see the point:

var obj = { foo: "xxx" };
for(key in obj) {
    alert($("#" + key).length); // 1   
}

<input id="foo"/>

http://jsfiddle.net/J4hC8/

I know this is old, but here is the solution. As stated by igor milla, you should use eval().

var test = "xxx";
alert(eval("test"));

Maybe what you need is

alert($("#" + test));

var test = "#xxx";
alert($(test));

Alternatively, you can use:

var test = "xxx";
alert($("#" + test));