加载页面后延迟执行函数的JavaScript

Question

我写了这个 javascript 来制作动画。它在主页上运行良好。我在最后写了一条警告信息。

如果我转到主页以外的地方，则必须出现此警告消息，但我收到警告消息，如果我删除该功能，警告消息在所有页面上都有效，我的代码有什么问题吗？

window.onload = function(){

    var yellows = document.getElementById('magazine-brief').getElementsByTagName('h2');
    var signUp = document.getElementById('signup-link');

        if (yellows != 'undefined' && signUp != undefined){
            function animeYellowBar(num){
                setTimeout(function(){
                    yellows[num].style.left = "0";
                    if(num == yellows.length-1){
                        setTimeout(function(){
                            signUp.style.webkitTransform = "scale(1)";
                        },num*250);
                    }

                }, num * 500);
            }
            for (var i = 0; i < yellows.length; i++){
                animeYellowBar(i);
            }
        }

    alert('hi');

}

Answer 1

• DEMO: http://jsbin.com/enaqu5/2

var yellows,signUp;
window.onload = function() {
    yellows = document.getElementById('magazine-brief').getElementsByTagName('h2');
    signUp = document.getElementById('signup-link');
    if (yellows !== undefined && signUp !== undefined) {
        for (var i = 0; i < yellows.length; i++) {
            animeYellowBar(i);
        }
    }
  alert('hi')
}
function animeYellowBar(num) {
    setTimeout(function() {
        yellows[num].style.left = "0";
        if (num == yellows.length - 1) {
            setTimeout(function() {
                signUp.style.webkitTransform = "scale(1)";
            },
            num * 250);
        }
    },
    num * 500);
}

• DEMO 2: http://jsbin.com/utixi4 (just for sake)

$(function() {
    $("#magazine-brief h2").each(function(i,item) {
          $(this).delay(i+'00').animate({'marginLeft': 0 }, 500 ,function(){
           if ( i === ( $('#magazine-brief h2').length - 1 ) )
             $('#signup-link')[0].style.webkitTransform = "rotate(-2deg)";
          });
    });
});