javascript - 从回调中访问属性

Question

我根据我在此处找到的解决方案将图像加载到内存中，这很好，但由于它位于回调内，因此属性宽度和高度在其外部未定义。

var originalWidth, originalHeight;
$("<img/>") // Make in memory copy of image to avoid css issues
    .attr("src", $(img).attr("src"))
    .load(function() {
        originalWidth = this.width;   // Note: $(this).width() will not
        originalHeight = this.height; // work for in memory images.
    });
console.log(originalWidth); // undefined obviously since `this` is only accessible within `load`s callback. 

我考虑过将它放在一个对象中，例如:

var originalWidth, originalHeight;
var imgDimensions = {};
$("<img/>") // Make in memory copy of image to avoid css issues
    .attr("src", $(img).attr("src"))
    .load(function() {
        imgDimensions.originalWidth = this.width;   // Note: $(this).width() will not
        imgDimensions.originalHeight = this.height; // work for in memory images.
    });
console.log(imgDimensions['originalWidth']); // undefined also

如何从 load() 中返回这些属性？

Answer 1

console.log 在加载函数触发之前执行，因此 originalWidth 尚未更新。