Type 1: Cyclic check replacement

// For consumer invocation
function trim(s){
  return trimRight(trimLeft(s));
}
// Remove the white space on the left
function trimLeft(s){
  if(s == null) {
    return "";
  }
  var whitespace = new String(" \t\n\r");
  var str = new String(s);
  if (whitespace.indexOf(str.charAt(0)) != -1) {
    var j=0, i = str.length;
    while (j < i && whitespace.indexOf(str.charAt(j)) != -1){
      j++;
    }
    str = str.substring(j, i);
  }
  return str;
}

// Remove the white space on the right  www.ofstack.com
function trimRight(s){
  if(s == null) return "";
  var whitespace = new String(" \t\n\r");
  var str = new String(s);
  if (whitespace.indexOf(str.charAt(str.length-1)) != -1){
    var i = str.length - 1;
    while (i >= 0 && whitespace.indexOf(str.charAt(i)) != -1){
      i--;
    }
    str = str.substring(0, i+1);
  }
  return str;
}

Type 2: Regular replacement

<SCRIPT LANGUAGE="JavaScript">
<!--
String.prototype.Trim = function()
{
return this.replace(/(^\s*)|(\s*$)/g, "");
}
String.prototype.LTrim = function()
{
return this.replace(/(^\s*)/g, "");
}
String.prototype.RTrim = function()
{
return this.replace(/(\s*$)/g, "");
}
//-->
</SCRIPT>

// Remove left space ;
function ltrim(s){
  return s.replace(/(^\s*)/g, "");
}
// Remove right space ;
function rtrim(s){
  return s.replace(/(\s*$)/g, "");
}
// Remove left and right spaces ;
function trim(s){
  return s.replace(/(^\s*)|(\s*$)/g, "");
}

Type 3: Using jquery

$.trim(str)

The internal implementation of jquery is:

function trim(str){
  return str.replace(/^(\s|\u00A0)+/,'').replace(/(\s|\u00A0)+$/,'');
}

Type 4: Using motools

function trim(str){
  return str.replace(/^(\s|\xA0)+|(\s|\xA0)+$/g, '');
}

Fifth: Clipping strings

function trim(str){
  str = str.replace(/^(\s|\u00A0)+/,'');
  for(var i=str.length-1; i>=0; i--){
    if(/\S/.test(str.charAt(i))){
      str = str.substring(0, i+1);
      break;
    }
  }
  return str;
}

//----------------------------------------------------------
//    Remove spaces before and after strings
//   Return value:
//   String after removing spaces
//----------------------------------------------------------
function trim(param) {
  if ((vRet = param) == '') { return vRet; }
  while (true) {
    if (vRet.indexOf (' ') == 0) {
      vRet = vRet.substring(1, parseInt(vRet.length));
    } else if ((parseInt(vRet.length) != 0) && (vRet.lastIndexOf (' ') == parseInt(vRet.length) - 1)) {
      vRet = vRet.substring(0, parseInt(vRet.length) - 1);
    } else {
      return vRet;
    }
  }
}