Queue.js预加载图像会一直等待吗? (打回来) [英] Queue.js to preload images is waiting forever? (Callback)

问题描述

我正在使用 mbostock queue.js脚本通过执行类似操作来加载多个json文件:

I'm using mbostock queue.js script to load several json files, by doing something like that:

var q = queue()
.defer(d3.json, "world-110m.json")
.defer(d3.tsv, "world-country-names.tsv")
.await(ready);

就绪是在加载所有文件时要执行的功能.

where ready is the function to execute when everythin is loaded.

我想通过添加一个延迟来预加载图像.这可能吗?我已经尝试了几种方法，但是没有用.

I would like to preload an image by adding a defer. Is this possible? I have tried it several ways, but it doesn't work.

我想必须创建一个函数，但是我不能使它异步，并且队列永远等待着……

I suppose that a function must be created, but I can't make it asynchronous, and the queue keeps waiting forever...

推荐答案

这是queue.js对回调:

Here is what queue.js is expecting from the callbacks:

回调遵循Node.js约定，其中第一个参数是可选的错误对象，第二个参数是任务的结果.

The callbacks follow the Node.js convention where the first argument is an optional error object and the second argument is the result of the task.

因此，您的代码的简单版本可能如下所示:

Thus a simple version of your code might look like this:

var loadImage = function(src, cb) {
    var img = new Image();
    img.src = src;
    img.onload  = function(){ cb(null, img); };
    img.onerror = function(){ cb('IMAGE ERROR', null); };
};

queue()
    .defer(d3.json, "data/flare.json")
    .defer(d3.csv, "data/test.csv")
    .defer(loadImage, "img/test.png")
    .await( function(error, jsondata, csvdata, imagedata) {
        if (error) { console.log('error', error); } 
        else { console.log('success', jsondata, csvdata, imagedata) }
    });

我不确定要返回关于图像的什么(如果有的话)，但是在上面的示例中，cb(null, img)我将返回整个对象.

I'm not sure what (if anything) you wanted to return about the image, but in the above example cb(null, img) I'm returning the whole object.

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