Load scripts asynchronously

async-script-load.js

// If you user jQuery: https://api.jquery.com/jQuery.getScript/
// $.getScript(url, successCallback)
$.getScript( "ajax/test.js", function( data, textStatus, jqxhr ) {
  console.log( data ); // Data returned
  console.log( textStatus ); // Success
  console.log( jqxhr.status ); // 200
  console.log( "Load was performed." );
});

// Handling Errors
$.getScript( "ajax/test.js" )
  .done(function( script, textStatus ) {
    console.log( textStatus );
  })
  .fail(function( jqxhr, settings, exception ) {
     console.log( "Triggered ajaxError handler." );
});

// For JavaScript
// REF: https://stackoverflow.com/questions/7718935/load-scripts-asynchronously/7719185#answer-7719185
function loadScript(src, callback) {
    var s,
        r,
        t;
    r = false;
    s = document.createElement('script');
    s.type = 'text/javascript';
    s.src = src;
    s.onload = s.onreadystatechange = function () {
        //console.log( this.readyState ); //uncomment this line to see which ready states are called.
        if (!r && (!this.readyState || this.readyState == 'complete')) {
            r = true;
            callback();
        }
    };
    t = document.getElementsByTagName('script')[0];
    t.parentNode.insertBefore(s, t);
}

loadScript(src, callback);