javascript - How to call the width and height of the read remote image

Question

I want to call the width and height of this image outside the function. How should I write it?
I've been stuck for three days and have no clue.

<code>    // 更新：
    // 05.27: 1、保证回调执行顺序：error > ready > load；2、回调函数this指向img本身
    // 04-02: 1、增加图片完全加载后的回调 2、提高性能

    /**
     * 图片头数据加载就绪事件 - 更快获取图片尺寸
     *
     * 原理：没有缓存的情况下，用计时器不断验证图片的大小是否发生变化，如果不在变化则为ready
     *       如果有缓存则w3c浏览器会调用 complete，ie则会走 onload，都不在走 计时器那部分
     *
     * @version    2011.05.27
     * @author    TangBin
     * @see        http://www.planeart.cn/?p=1121
     * @param    {String}    图片路径
     * @param    {Function}    尺寸就绪
     * @param    {Function}    加载完毕 (可选)
     * @param    {Function}    加载错误 (可选)
     * @example imgReady('http://www.google.com.hk/intl/zh-CN/images/logo_cn.png', function () {
alert('size ready: width=' + this.width + '; height=' + this.height);
});
     */
    var imgReady = (function () {
        var list = [], intervalId = null,

            // 用来执行队列
            tick = function () {
                var i = 0;
                for (; i < list.length; i++) {
                    list[i].end ? list.splice(i--, 1) : list[i]();
                }
                ;
                !list.length && stop();
            },

            // 停止所有定时器队列
            stop = function () {
                clearInterval(intervalId);
                intervalId = null;
            };

        return function (url, ready, load, error) {
            var onready, width, height, newWidth, newHeight,
                img = new Image();

            img.src = url;

            // 如果图片被缓存，则直接返回缓存数据
            if (img.complete) {
                ready.call(img);
                load && load.call(img);
                return;
            }
            ;

            width = img.width;
            height = img.height;

            // 加载错误后的事件
            img.onerror = function () {
                error && error.call(img);
                onready.end = true;
                img = img.onload = img.onerror = null;
            };

            // 图片尺寸就绪
            onready = function () {
                newWidth = img.width;
                newHeight = img.height;
                if (newWidth !== width || newHeight !== height ||
                    // 如果图片已经在其他地方加载可使用面积检测
                    newWidth * newHeight > 1024
                    ) {
                    ready.call(img);
                    onready.end = true;
                }
                ;
            };
            onready();

            // 完全加载完毕的事件
            img.onload = function () {
                 // onload在定时器时间差范围内可能比onready快
                // 这里进行检查并保证onready优先执行
                !onready.end && onready();

                load && load.call(img);

                // IE gif动画会循环执行onload，置空onload即可
                img = img.onload = img.onerror = null;
            };

                // 加入队列中定期执行
            if (!onready.end) {
                list.push(onready);
                // 无论何时只允许出现一个定时器，减少浏览器性能损耗
                if (intervalId === null) intervalId = setInterval(tick, 40);
            }
            ;
        };
    })();</code>

<code>    var img_url = 'http://www.planeart.cn/demo/imgReady/vistas24.jpg';
    imgReady(img_url, function () {
        alert(this.width + '\n' + this.height);
        document.getElementById('song').src = img_url;

    })</code>

This kind of pop-up width and height is possible, but how to call this width and height.
Your few codes can save me a lot of time, thank you very much

Answer 1

Callback

<code>function yourFun(width,height){
    console.log(width,height)
}
var img_url = 'http://www.planeart.cn/demo/imgReady/vistas24.jpg';
    imgReady(img_url, function () {
        yourFun(this.width , this.height);
        document.getElementById('song').src = img_url;

    })</code>

I don’t know if I understand it correctly

Answer 2

It seems that this problem cannot be solved. This image reading function is somewhat similar to the asynchronous ajax, and its assignment is executed later