javascript - 使用窗口从字符串执行函数不起作用

Question

我正在尝试使用包含函数名称的字符串来执行函数。

Several resources I've found建议这样的事情:

function runMe(){alert("fail"));
var fnstring = "runMe";
var fn = window[fnstring];
fn();

但是，它对我来说根本不起作用( JSFiddle demo )。我最终得到的 fn 为未定义。我是否做错了什么，或者窗口行为发生了变化？

Answer 1

由于提升，您收到 Uncaught TypeError: undefined is not a function 错误。查看您提供的第一个链接，您的版本与他们的版本之间有一个关键区别:条件。

Your (second) version :

function runMe(thething) {
    alert("the function has successfully run: " + thething);
}

// function we want to run
var fnstring = "runMe";
alert("string: " + fnstring);

// find object
var fn = window[fnstring]("lkjlksdfsdfj");
alert("function: " + fn);

// is object a function?
alert("is function?: " + typeof fn === "function");
fn();

My version, working without errors :

function runMe(thething) {
    console.log("the function has successfully run: " + thething);
}

// function we want to run
var fnstring = "runMe";

// find object
var fn = window[fnstring]("lkjlksdfsdfj");

// is object a function?
if (typeof fn === "function") fn();

您的版本抛出错误的原因是它被提升为如下所示:

function runMe(thething) {
    alert("the function has successfully run: " + thething);
}

var fnstring, fn;

fn();

fnstring = "runMe";
fn = window[fnstring]("lkjlksdfsdfj");

所以当它被调用时，它不是一个函数；这是一个 undefined variable 。

另一方面，据我了解提升，我的版本被提升如下:

function runMe(thething) {
    console.log("the function has successfully run: " + thething);
}

var fnstring, fn;
fnstring =  = "runMe";
fn = window[fnstring]("lkjlksdfsdfj");

if (typeof fn === "function") fn();

这样，当函数被实际调用时，一切就都准备好了。