滚动100个像素后的jQuery警报 [英] jQuery alert after 100 pixels scrolled

问题描述

用户滚动100像素后是否可以触发警报。

Is it possible to fire an alert after a user scrolls 100 pixels.

这是我到目前为止所得到的，但我知道我遗失了一些东西;

Here's what I have so far but I know I'm missing something;

$(window).scroll(function() {
    if (document.documentElement.clientHeight + 
        $(document).scrollTop() == "100px")
    { 
        alert("You've scrolled 100 pixels.");
    }
});

推荐答案

查看窗口.scrollTop（返回一个整数） ：

Look at the window .scrollTop (returns an integer):

$(window).scroll(function() {
    if ($(this).scrollTop() === 100) { // this refers to window
        alert("You've scrolled 100 pixels.");
    }
});

但如果您滚动了102px则不会触发警报框。

but if you have scrolled 102px it wont trigger the alert box.

如果您只想触发警报，一旦有一个全局变量设置为true，如果它被触发：

if you just want to trigger the alert once have a global variable that sets to true if it has been trigged:

$(function(){
    var hasBeenTrigged = false;
    $(window).scroll(function() {
        if ($(this).scrollTop() >= 100 && !hasBeenTrigged) { // if scroll is greater/equal then 100 and hasBeenTrigged is set to false.
            alert("You've scrolled 100 pixels.");
            hasBeenTrigged = true;
        }
    });
});

或者仅在触发警报框后取消绑定滚动事件：

or just unbind the scroll event once the alert box has been trigged:

$(function(){
    $(window).bind("scroll.alert", function() {
        var $this = $(this);
        if ($this.scrollTop() >= 100) {
            alert("You've scrolled 100 pixels.");
            $this.unbind("scroll.alert");
        }
    });
});

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