Aborting the xmlhttprequest

Question

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

Answer 1

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

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

Example: http://jsfiddle.net/wJt8A/

---

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);

Example: http://jsfiddle.net/rC63r/1/

Answer 2

You should be able to reference the "this" keyword in your canceledUpload event handler. That refers to the XMLHttpRequest. Put this in the handler:

this.abort();

Answer 3

Abort all XMLHttpRequest:

var array_xhr = new Array();
function uploadFile(){ 
    ...
    var xhr = new XMLHttpRequest(); 
    array_xhr.push(xhr);
    ...
}

function abort_all_xhr(){
  if (array_xhr.length>0) {
        for(var i=0; i<array_xhr.length; i++){
            array_xhr[i].abort();
        }
        array_xhr.length = 0;
    };
}

abort_all_xhr();

Answer 4

You can use AbortController and fetch to abort requests.

Demo

Code

const btn = document.getElementById('btn');
const btn2 = document.getElementById('btn2');
const url = 'https://www.mocky.io/v2/5185415ba171ea3a00704eed?mocky-delay=1000ms';

const ctrl;

btn.addEventListener('click', e => {
  ctrl = new AbortController();
  const signal = ctrl.signal;

  fetch(url, { signal })
    .then(r => r.json())
    .then(r => {
      console.log('Request result', r);
    }).catch(e => {
      console.error('Request was aborted. Error:', e);
    })
});

btn2.addEventListener('click', e => {
  ctrl.abort();
});