Stupid syntax difference between IE and Firefox

When you are doing javascript/AJAX development you probably will add a very useful function trim() into build-in String object to return a copy of a string without both leading and trailing spaces. To do so you just need simply add one sentence in front of your js file. Below is the coding I used in my js framework.

function String.prototype.trim() {return this.replace(/(^\s*)|(\s*$)/g,"");};

Unfortunately this sentence only works on IE browser. It caused an error on Firefox which cost me one hour this afternoon to figure it out. after I changed the sentence to the syntax shown below a peaceful world came back again.

String.prototype.trim = function() {return this.replace(/(^\s*)|(\s*$)/g,"");};

It is painful to find out these tiny differences and it always lets me down. :(  But from the positive side, it makes you always use the standard syntax rule to build your project.