lib/functions/lookup.js
function lookup(name){
  utils.assertType(name, 'string', 'name');
  var node = this.lookup(name.val);
  if (!node) return nodes.null;
  return this.visit(node);
}
function lookup(name){
  utils.assertType(name, 'string', 'name');
  var node = this.lookup(name.val);
  if (!node) return nodes.null;
  return this.visit(node);
}
function lookup ( name ) { utils . assertType ( name , 'string' , 'name' ) ; var node = this . lookup ( name . val ) ; if ( ! node ) return nodes . null ; return this . visit ( node ) ; }
Lookup variable `name` or return Null.

@param {String} name
@return {Mixed}
@api public
Lookup variable name or return Null .