//Function to trim the space in the left side of the string
String.prototype.ltrim = function (){
  return this.replace(/^\s*/, "" );
}

//Function to trim the space in the right side of the string
String.prototype.rtrim = function(){
   return this.replace( /\s*$/, "" );
}

//Function to trim the space in the  string
String.prototype.trim = function() {
   return this.rtrim().ltrim();
}
 

alert("   Hello   ".trim())