CODEWITHSUNDEEP
javascriptnode.jshttplong-polling
MarijnS95
MarijnS95

Reputation: 4793

Simple XHR long polling without jQuery

I am trying to wite a simple long polling system (yep, I do not want to use any ready-made scipt, as I want to learn from it). I am using a node server where I can easily pipe/write my data back to the client without calling result.end();. How should I do this client side? I just want this as a simple and not really good fallback for users using ie<=9, as the better browsers get a fast and easy to use websocket.

Long question short: How to do long-polling in plain JS without jQuery or other framework? (Or is there a better way than long-polling).

Upvotes: 3

Views: 5574

Answers (1)

Arthur Weborg
Arthur Weborg

Reputation: 8580

Is the following what you are looking for?

  var xhr = new XMLHttpRequest();
  xhr.responseType = 'blob';//or 'text', 'json', ect. there are other types. 
  xhr.timeout = 60000;//milliseconds until timeout fires. (1 minute)
  xhr.onload = function(e2){
    var blob = xhr.response;
    //handle response data
  }
  xhr.ontimeout = function(){
    //if you get this you probably should try to make the connection again.
    //the browser should've killed the connection. 
  }
  xhr.open('GET', "/path/to/URL.cmd?param1=val1&param2=val2", true);
  xhr.send();

I think the timeout attribute is the key to making the long-polls work, for more see the spec there are more information on the responseType's in the same document. If timeout is not specified, it's default value is zero.

Upvotes: 2

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