CODEWITHSUNDEEP
javascriptdom-events
deepmoteria
deepmoteria

Reputation: 2441

Checking of internet connection by requesting an image does not work after the image gets cached in the browser

Checking of internet connection by requesting an image does not work after the image gets cached in the browser. After one or two time, this doesn't work as the image is stored in the browser's cache so is there any solution for that? Or what do I need to check whether a connection is available or not? window.navigator.online is not reliable. so looking for the other interesting and reliable solution.

Upvotes: 0

Views: 156

Answers (3)

deepmoteria
deepmoteria

Reputation: 2441

The perfect solution for checking internet connectivity is to give a ajax call to your server to the dummy page and make that dummy page's entry in the application cache manifest file in the network section so that it may not get cached in the browser, otherwise it wl take that file from browser and show you as online even if u are in offline mode.

Upvotes: 0

Andrew D.
Andrew D.

Reputation: 8230

Using XMLHttpRequest object and POST protocol. POST-request does not cached. But this works only if image (or any other resource) loaded from the same domain as page (XMLHttpRequest limitation).

var xhr = new XMLHttpRequest();
xhr.open("POST", "url_for_image_file", true);
xhr.onreadystatechange = function() {
    if(xhr.readyState === 4)
      if(xhr.status!==200) {
        // no image loaded
        alert("fail connect to server");
      }
      else {
        alert("connection success");
      }
};
xhr.send(null);

Upvotes: 1

epascarello
epascarello

Reputation: 207521

Use a cache buster querystring. The querystring forces the browser to check the servver for the new image.

yourImageObj.src = "newImage.png?time=" + new Date().getTime();

Upvotes: 3

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