find id of input(text) in asp.net

function getID()
{
   var coltrols = document.getElementByTagName('input');
   var id="";
   for(var i=0;i<controls.length;i++)
   {
      if(controls[i].value == 'your value')
      {
          id=controls[i].name;
          break;
      }
   }
  
   return id;
}