function addLoadEvent(func) {
    'use strict';
    var oldonload = window.onload;
    if (typeof window.onload !== 'function') {
        window.onload = func;
    } else {
        window.onload = function() {
            oldonload();
            func();
        };
    }
}
function addLoadEvent(func) {
    'use strict';
    var oldonload = window.onload;
    if (typeof window.onload !== 'function') {
        window.onload = func;
    } else {
        window.onload = function() {
            oldonload();
            func();
        };
    }
}
function addLoadEvent ( func ) { 'use strict' ; var oldonload = window . onload ; if ( typeof window . onload !== 'function' ) { window . onload = func ; } else { window . onload = function ( ) { oldonload ( ) ; func ( ) ; } ; } }
event listener: DOM ready
event listener : DOM ready