Update: This advice is now totally out-of-date and wrong. Just use replace. As recent Browserscope results show, all browsers have optimized replace to be much faster than split/join. Thanks to Luigi van der Pal for pointing this out in the comments!

When trying to do a find-and-replace in Javascript with static search and replace strings, it’s always faster to use String.split() and String.join() than to use String.replace(). Compare:

var myString = '......some long text.....'; 
mystring.replace(/,/g,"; "); // Replace the commas with semi-colon-space

with

mystring.split(",").join("; "); // Replace the commas with semi-colon-space

The latter split/join method will always be faster. Note that this is only useful for static find-and-replace. For instance, you could not do anything like the following with splits and joins:

mystring.replace(/^[0-9]+([A-Za-z]*)/g, "$1");

Of course, you could also use this method to strip characters out of a string:

mystring.split(",").join('');

Good luck!