What about using this?:
http://jsfiddle.net/RMaNd/8/
var mystring = "http://www.google.com/?v=as12&&src=test&img=test";
mystring = mystring.replace(/&src=.+&/, ""); // Didn't realize it isn't necessary to escape "&"
alert(mystring);
This assumes that "any" character will come after the "=" and before the next "&", but you can always change the . to a character set if you know what it could be - using [ ]
This also assumes that there will be at least 1 character after the "=" but before the "&" - because of the +. But you can change that to * if you think the string could be "src=&img=test"
UPDATE:
Using split might be the correct choice for this problem, but only if the position of src=whatever is still after "&&" but unknown...for example, if it were "&&img=test&src=test". So as long as the "&&" is always there to separate the static part from the part you want to update, you can use something like this:
http://jsfiddle.net/Y7LdG/
var mystring1 = "http://www.google.com/?v=as12&&src=test&img=test";
var mystring2 = "http://www.google.com/?v=as12&&img=test&src=test";
var final1 = removeSrcPair(mystring1);
alert(final1);
var final2 = removeSrcPair(mystring2);
alert(final2);
function replaceSrc(str) {
return str.replace(/src=.*/g, "");
}
function removeSrcPair(orig) {
var the_split = orig.split("&&");
var split_second = the_split[1].split("&");
for (var i = split_second.length-1; i >= 0; i--) {
split_second[i] = replaceSrc(split_second[i]);
if (split_second[i] === "") {
split_second.splice(i, 1);
}
}
var joined = split_second.join("&");
return the_split[0] + "&" + joined;
}
This still assumes a few things - the main split is "&&"...the key is "src", then comes "=", then 0 or more characters...and of course, the key/value pairs are separated by "&". If your problem isn't this broad, then my first answer seems fine. If "src=test" won't always come first after "&&", you'd need to use a more "complex" Regex or this split method.