Checking if a URL is broken in Javascript

This question has been posted on Stack before, but none so specific as to what I'm trying to understand.

The simplest way to check if a URL is corrrect to send a http Head request. But how do you use that to specify the URL ?

I found this in a previous post :

function UrlExists(url) {
  var http = new XMLHttpRequest();
  http.open('HEAD', url, false);
  http.send();
  return http.status!=404;
}

But it doe开发者_如何学运维sn't seem to run in firebug for a few reasons.

My apologies ahead of time for being daft.

I'd recommend to use jQuery for correct cross-browser ajax requests:

function UrlExists(url, cb){
    jQuery.ajax({
        url:      url,
        dataType: 'text',
        type:     'GET',
        complete:  function(xhr){
            if(typeof cb === 'function')
               cb.apply(this, [xhr.status]);
        }
    });
}

Usage:

UrlExists('/path/script.pl', function(status){
    if(status === 200){
       // file was found
    }
    else if(status === 404){
       // 404 not found
    }
});

Modern, cross and short way

checkLink = async url => (await fetch(url)).ok

which is same of:

async checkLink(url) { return (await fetch(url)).ok }

which is same of:

async function checkLink(url) { return (await fetch(url)).ok }

which is same of:

Note: Starting with Gecko 30.0 (Firefox 30.0 / Thunderbird 30.0 / SeaMonkey 2.27), Blink 39.0, and Edge 13, synchronous requests on the main thread have been deprecated due to their negative impact on the user experience.

Cross solution (old, deprecated)

function UrlExists(url) {
 var http = new XMLHttpRequest();
 http.open('HEAD', url, false);
 http.send();
 return http.status==200;
}