Javascript 检测浏览器滚动到顶部？

Question

如何修改以下代码来检测滚动到首页。

window.onscroll = function(ev) {
    if ((window.innerHeight + window.scrollY) >= document.body.offsetHeight) {
        alert(bottom);
    }
};

编辑:

顺便说一下，我正在为 Windows Phone 8 开发 IE 10

Answer 1

设法搞清楚了。这是我的代码:

window.onscroll = function() {

    var body = document.body; //IE 'quirks'
    var document = document.documentElement; //IE with doctype
    document = (document.clientHeight) ? document : body;

    if (document.scrollTop == 0) {
        alert("top");
    }        
};

检查它是否正在运行:

window.onscroll = function(){

    var B = document.body; //IE 'quirks'
    var D = document.documentElement; //IE with doctype
    D = (D.clientHeight)? D: B;
    
    if (D.scrollTop == 0){
        alert("top");
    }        
};

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EXPLANATION OF HOW THIS CODE WORKS:

window.onscroll is the command to assign the onscroll event tothe window element.

Now, as the onscroll event gets fired when an element's scrollbaris being scrolled., the element will be the window itself in thiscase.

Now, the function will be called when the event is fired.

In the function, we get the "document.body" to as en IE is the way toget it. After this, we get the documentElement, if there is a doctype.

Then, this line, is the one that chooses between the document or thebody if the document.clientHeight is informed. If it's informed, itwill put document on variable document. If not, it will put the bodyitself.After this, it will check the scrollTop property in order to knowif current scroll position is "at the top"