function lTrim(s) {
 if (s != null && typeof("s") != "undefined" && s.length >  0 ) {
  while (s.length >  0  && s.charAt( 0 ) == ' ') {
   s = s.substr( 1 );
  }
 }
 return s;
}
function rTrim(s) {
 if (s != null && typeof("s") != "undefined" && s.length >  0 ) {
  while (s.length >  0  && s.charAt(s.length -  1 ) == ' '){
   s = s.substr( 0 , s.length -  1 );
  }
 }
 return s;
}
function trimAll(s){
 return lTrim(rTrim(s));
}

//или
function trim(s) {
  var i,j;
  for (i =  0 ; i < s.length && s.charAt(i) == " "; i++);
  for (j = s.length- 1 ; j >=  0  && s.charAt(j) == " "; j--);
  return s.substring(i, j+ 1 );
}