JavaScript - 无法读取 null 的属性“top" [英] JavaScript - Cannot read property 'top' of null

问题描述

我有滚动到列表中锚点位置的功能

I have function that scrolls to a anchor position in a list

   function snapToAnchor(anchor) {
    $('#divProductScroll').scrollTop(0);
    var offset = $(anchor).offset().top - $('#divProductScroll').offset().top;
    $('#divProductScroll').scrollTop(offset);
    //$('#divProductScroll').animate({ scrollTop: offset }, 250);
}

但这有时会给我带来错误

but this is giving me error some times

说无法读取 null 的属性 'top'

我不太擅长 JavaScript

I am not so good with JavaScript

有人可以帮忙解决这个问题吗?

Can any one help with this issue?

我发现了问题.

---

这个 snapToAnchor 函数在一个对话框模型中，所以当我第二次点击这个函数时，没有生成列表，这就是为什么我有空值，所以我做的是在触发这个函数之前，我重新创建了模态，然后进入函数，现在没有 null 的作用域.

I found the Problem.

---

This snapToAnchor function is in a dialog model, so second time when i hit this function, there is not list generated, that's why i have null value, so what i did is before firing this function, i recreate the modal and then step in to the function, now no scope of null.

推荐答案

锚变量不包含您站点的有效选择器.对此调用 offset 将返回 null.

The anchor variable does not contain a valid selector for you site. Calling offset on this will return null.

示例

var a = $('#non-existing-id'); //returns empty object
var b = a.offset(); // returns null
b.top; //throws a TypeError exception

您可以通过在第 3 行插入 alert(anchor) 来简单地调试您的程序.这将显示变量的内容.

You can simply debug your program by inserting alert(anchor) on line 3. This will show you the contents of the variable.

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