支持事件的图像预加载器javascript

我正在尝试找到一个图像预加载器脚本.

虽然我发现了一些,但它们都不支持在预加载完成时触发的事件.

有谁知道会这样做的任何脚本或jQuery插件？

希望这个问题适合stackoverflow – 如果没有,请随时将其删除.

解决方法:

这是一个从数组中预加载图像并在最后一个完成后调用回调的函数：

function preloadImages(srcs, imgs, callback) {
    var img;
    var remaining = srcs.length;
    for (var i = 0; i < srcs.length; i++) {
        img = new Image();
        img.onload = function() {
            --remaining;
            if (remaining <= 0) {
                callback();
            }
        };
        img.src = srcs[i];
        imgs.push(img);
    }
}

// then to call it, you would use this
var imageSrcs = ["src1", "src2", "src3", "src4"];
var images = [];

preloadImages(imageSrcs, images, myFunction);

而且由于我们现在正处于使用promises进行异步操作的时代,这里是上面的一个版本,它使用promises并通过ES6标准承诺通知调用者：

function preloadImages(srcs) {
    function loadImage(src) {
        return new Promise(function(resolve, reject) {
            var img = new Image();
            img.onload = function() {
                resolve(img);
            };
            img.onerror = img.onabort = function() {
                reject(src);
            };
            img.src = src;
        });
    }
    var promises = [];
    for (var i = 0; i < srcs.length; i++) {
        promises.push(loadImage(srcs[i]));
    }
    return Promise.all(promises);
}

preloadImages(["src1", "src2", "src3", "src4"]).then(function(imgs) {
    // all images are loaded now and in the array imgs
}, function(errImg) {
    // at least one image failed to load
});

而且,这是一个使用2015 jQuery承诺的版本：

function preloadImages(srcs) {
    function loadImage(src) {
        return new $.Deferred(function(def) {
            var img = new Image();
            img.onload = function() {
                def.resolve(img);
            };
            img.onerror = img.onabort = function() {
                def.reject(src);
            };
            img.src = src;
        }).promise();
    }
    var promises = [];
    for (var i = 0; i < srcs.length; i++) {
        promises.push(loadImage(srcs[i]));
    }
    return $.when.apply($, promises).then(function() {
        // return results as a simple array rather than as separate arguments
        return Array.prototype.slice.call(arguments);
    });
}

preloadImages(["src1", "src2", "src3", "src4"]).then(function(imgs) {
    // all images are loaded now and in the array imgs
}, function(errImg) {
    // at least one image failed to load
});

标签：preloading,javascript,jquery,image,preloader
来源： https://codeday.me/bug/20190915/1805348.html