Javascript ping | Paulʼs blog

Blog ≫ 2011 ≫ Javascript ping

Wed Sep 21

For work I needed to "ping" one website from another just using javascript - we have a customer on site A, and we want to send them to site B, but what if site B is broken? Let's send them somewhere else. So how do we tell if site B is up and running, and visible from where they are (in case, SAY, their DNS is broken). I found this ¹ and I adapted it to my needs like so:

var ping = { // ²
      preload: null,
      timer: null,
      ping: function ( img, success, fail ) {
        var sess = new Date();
        var nocache = sess.getTime();
        var uri = img+"?time="+nocache;
        ping.preload = new Image();
        ping.preload.onload = function() {
            clearTimeout(ping.timer);
            ping.timer = null;
            success( img );
        };
        ping.preload.src = uri;
        ping.timer = setTimeout( function ( ) {
          clearTimeout( ping.timer );
          ping.timer = null;
          ping.preload = null;
          fail( img );
        }, 3000 );
      }
    };

then to use it

ping.ping( 'http://foo.com', success_function, fail_function );

so something like

ping.ping( 'http://foo.com/img.png',
      function( img ) { alert( img + ' success' ) },
      function( img ) { alert( img + ' failed' ) }
    );

Removed old crynobone.com/ ci/ index.php/ archive/ view/ 852 link here.
Man alive it's weird looking at old code again, look at all that whitespace, semicolons, and inconsistent indenting

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