JavaScript - Trim a string

I need to trim strings in JavaScript every day and everytime I forgot the code snippet that do that so here is

/**Trims a string
*@param {String} str - the string to trim
*@return {String} the trimmed string
**/
function trim(str){
   var res = str.replace(/^\s+/, '');
   res = res.replace(/\s+$/, '');

   return res;
}

Pfui, now it's here forever.