用eval（）函数获取数组的长度？(getting the length of an array with eval()

用eval（）函数获取数组的长度？(getting the length of an array with eval()-function?)

为什么这不起作用：

var problem_0 = ["a","b","c","d"]; arrayname = "problem_0"; arraylength = eval([arrayname]).length; for (i = 0; i < arraylength; i++) {

我正在尝试根据用户点击的内容检索不同的数组，所以我需要arrayname是一个字符串，我可以修改一个字符串宽度代码。 eval（[arrayname]）。length返回“1”。 为什么？

Why doesnt this work:

var problem_0 = ["a","b","c","d"]; arrayname = "problem_0"; arraylength = eval([arrayname]).length; for (i = 0; i < arraylength; i++) {

I'm trying to retrieve different arrays depending on what the user click on, so i need arrayname to be a string, a string I can modify width a code. eval([arrayname]).length returns "1". Why?

最满意答案

如果数组具有全局范围，则无需使用eval 。

var problem_0 = ["a","b","c","d"]; arrayname = "problem_0"; alert(window[arrayname].length);

你也可以用this

var a = [1,2]; var b = "a"; alert(this[b].length); //outputs 2

No need to use eval if the array has a global scope.

var problem_0 = ["a","b","c","d"]; arrayname = "problem_0"; alert(window[arrayname].length);

you can also use this

var a = [1,2]; var b = "a"; alert(this[b].length); //outputs 2