javascript replace string in js file

I think you're going about it the wrong way. If notice is a variable in the global space you can just replace it normally.

window.someObject.notice = window.someObject.notice.replace("&sid=","&sid="+kwd); 

This will of course only work if notice is a variable that is navigable to in the global namespace and is not inside a closure. It is inside a closure if it has a var declaration inside a function() {...}

But, assuming that there is global access to that variable, that will be your easiest way to achieve this.

If not, you can try grabbing the contents of the script and executing it hopefully overwriting the original code. This will only work if your script and the script you are fetching are from the same origin (domain, subdomain, port, protocol, a few other things) - it is impossible otherwise due to the _Same Origin Policy_

Assuming you are at the same origin, you could do something like this (using jquery for simplicity)

( function() {
// First we need the url of the script, we can grab it out of the element directly or it can be hard coded
var scriptLocation = $('script#the-id-of-the-script-element').prop('src');

// Now that we have the location fetch the script again so we can get it as plaintext
// this will usually not do another HTTP request since your browser has it cached
$.get(scriptLocation).done(function(text) {  // I prefer the deferred syntax as being more explicit, this is equivalent to $.get(scriptLocation, function(text) {
  var newText = text.replace("&sid=","&sid="+kwd); 
  eval(newText);
});
} )()

Something like this could work.

try regex: (not tested)

myregexp = new RegExp("/&sid=/", "gims");
str.replace(myregexp, "&sid=" + kwd);