javascript - 无法读取未定义的属性 'length'

Question

for (i = 0; i < count; i++) {
    var item = list.childNodes[i]._value;
    var RecID = item.RecID;
    var zerocount = 5 - RecID.length;
    var PicZeros = "";
    for (k = 0; k < zerocount; k++)
        PicZeros += "0";
    var url = "/p_" + PicZeros + RecID + "_01.jpg";
}

我收到此错误:

TypeError: Cannot read property 'length' of undefined 

我不明白如何解决这个问题？

Answer 1

好吧，在某些时候，list.childNodes[i]._value.RecID 会给你一个未定义的值。

这是您问题的根本原因，您需要解决它。

也许count是错误的，也许你已经错误地填充了列表，我们无法从给出的代码中真正看出。

And, as an aside, I'm almost certain there's better ways to left-pad a string with 0 characters than with a loop. Something like:

var url = "/p_" + "00000".substring(RecID.length) + RecID + "_01.jpg";

would be better.