How to change this ajax code to long polling [duplicate]

问题

This question already exists:

How to change from ajax polling to long polling [duplicate]

Closed 6 years ago.

This is my ajax code so please can anyone tell me how can i change this code to long polling ?

Here is my code :-

var chat = {}
chat.fetchMessages = function () {
  $.ajax({
    url: 'ajax/ajax/chat.php',
    type: 'POST',
    data: { method: 'fetch' },
    success: function(data) {
      $('#chats').html(data);
    }
  }); 
}
chat.interval = setInterval(chat.fetchMessages, 1000);

回答1:

You have to put the next call of fetchMessage in the callback of the previous one :

var chat = {}
chat.fetchMessages = function () {
  $.ajax({
    url: 'ajax/ajax/chat.php',
    type: 'POST',
    data: { method: 'fetch' },
    success: function(data) {
      $('#chats').html(data);
      chat.fetchMessages(); // let's do it again
    }
  }); 
}
chat.fetchMessages(); // first call

回答2:

The above code seems to work fine but this will call function immediately as a result of this it would increase the traffic and possibly for continuous long polling memory usage by the browser will increase . Try to use settimeout to keep some duration between calls made , would be good if you clear cache too . Other option would be comet or signaR .

来源：https://stackoverflow.com/questions/15838715/how-to-change-from-ajax-polling-to-long-polling