中止 xmlhttprequest-前端问题

Aborting the xmlhttprequest(中止 xmlhttprequest)

本文介绍了中止 xmlhttprequest的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！

问题描述

我正在使用 HTML5 上传文件.我有一个按钮单击事件附加到函数 uploadFile().它工作正常.我还有一个单独的按钮来取消上传.我知道我们需要调用 xhr.abort() 但如何访问 uploadCanceled 函数中的 xhr 对象?我可以使 xhr 对象成为全局对象，但这不是正确的方法.有人可以在这里指导我吗?


I am using HTML5 for uploading files. I have a button click event attached to the function uploadFile(). It works fine. I also have a separate button to cancel the upload. I know we need to call xhr.abort() but how do I access the xhr object in the uploadCanceled function? I can make the xhr object global but that is not the proper way. Can someone guide me here?
function uploadFile(){ 
    var filesToBeUploaded = document.getElementById("fileControl"); 
    var file = filesToBeUploaded.files[0]; 
    var xhr= new XMLHttpRequest(); 
    xhr.upload.addEventListener("progress", uploadProgress, false);
    xhr.addEventListener("load", uploadComplete, false);
    xhr.addEventListener("error", uploadFailed, false);
    xhr.addEventListener("abort", uploadCanceled, false);


    xhr.open("POST", "upload.php", true); 

    var fd = new FormData();
    fd.append("fileToUpload", file);
     xhr.send(fd); 
}


    function uploadCanceled(evt) {
        alert("Upload has been cancelled");
    } 

干杯
推荐答案

addEventListener 将设置 uploadCanceled 的上下文 (this) 为 <代码>xhr:

addEventListener will set the context (this) of uploadCanceled to xhr:

function uploadCanceled(evt) {
    console.log("Cancelled: " + this.status);
}

示例:http://jsfiddle.net/wJt8A/

如果您需要通过取消"单击触发 xhr.abort，则可以返回引用并在此之后添加所需的任何侦听器:

If, instead, you need to trigger xhr.abort through a "Cancel" click, you can return a reference and add any listeners you need after that:

function uploadFile() {
    /* snip */
    xhr.send(fd);

    return xhr;
}

document.getElementById('submit').addEventListener('click', function () {
    var xhr = uploadFile(),
        submit = this,
        cancel = document.getElementById('cancel');

    function detach() {
        // remove listeners after they become irrelevant
        submit.removeEventListener('click', canceling, false);
        cancel.removeEventListener('click', canceling, false);
    }

    function canceling() {
        detach();
        xhr.abort();
    }

    // detach handlers if XHR finishes first
    xhr.addEventListener('load', detach, false);

    // cancel if "Submit" is clicked again before XHR finishes
    submit.addEventListener('click', canceling, false);

    // and, of course, cancel if "Cancel" is clicked
    cancel.addEventListener('click', canceling, false);
}, false);

示例:http://jsfiddle.net/rC63r/1/

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