setInterval runs continuously in Firefox on Android

Question

I have a short snippet of Javascript which I want to poll a server every couple of seconds and update the DOM.

function updateCard() {    
    var xhttp = new XMLHttpRequest();
    xhttp.onreadystatechange = function() {
        if (this.readyState == 4 && this.status == 200) {
            card = JSON.parse(this.responseText);
            document.getElementById("season").innerHTML = card.season;
        }                  
    };                     
    xhttp.open("GET", "/curr_card/", true);
    xhttp.send();
}
window.onload = updateCard;
window.setInterval(updateCard,2000);

On most browsers that's what happens. There are a few one-off calls to updateCard, but on the whole the server shows ~1/2 connection per second per client.

However, when I access the page in Firefox on Android (49.0) the browser starts continuously polling /curr_card/, tens of times a second.

I've seen people suggest replacing the setInterval line with window.setInterval(function() {updateCard();},2000);, this doesn't help.

I'm pretty new to Javascript and AJAX, so have no idea why this is happening. Is it a bug in FF? I can post more code if requested.

Thanks in advance.

Answer 1

After testing and discussing in OP's comments, we concluded this must be an issue specific to Firefox on the OP's HTC M7, as it could not be reproduced on the same version Firefox on a Galaxy S7.