Javascript - load script dynamically and execute it

            // Load Javascript dynamically
            if (autonumberlinks) {
              var secondScript = document.createElement('script');
              secondScript.type = 'text/javascript';
              secondScript.src = 'test_hash.js';
                secondScript.onload = function() {
                // code to execute after the second script is loaded and executed
                addHashLabels(); // function of the dynamic loaded file
              };
              document.head.appendChild(secondScript);
            }