带返回的image.onload函数 [英] image.onload function with return

问题描述

我有一个JS函数，其中计算了一个值，并且应该返回此值但是我每次都得到 undefined 但是如果我 console.log（ ）此函数中的结果是否有效。你能帮帮忙吗？

I have a JS function where a value is computed and this value should be returned but I get everytime undefined but if I console.log() the result within this function it works. Could you help?

function detect(URL) {
    var image = new Image();
    image.src = URL;
    image.onload = function() {
        var result = [{ x: 45, y: 56 }]; // An example result
        return result; // Doesn't work
    }
}

alert(detect('image.png'));

推荐答案

我自己拿到：

我不知道我可以为其分配一个变量（对于我看起来已经分配）onload。

I didn't know that I can assign a variable to that (for me looking already assigned) onload.

function detect(URL) {
    var image = new Image();
    image.src = URL;
    var x = image.onload = function() {
        var result = [{ x: 45, y: 56 }]; // An example result
        return result;
    }();
    return x;
}

alert(detect('x'));

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