Some node modules are making use of these functions.

It could also be added by nodejar initialization scripts:
if (!String.prototype.trimLeft) {
   String.prototype.trimLeft = function(){
     return this.replace(/^\s+/, '');
   }
 }
 
 if (!String.prototype.trimRight) {
   String.prototype.trimRight = function(){
     return this.replace(/\s+$/, '');
   }
 }