Detect if data changed on jQuery.load()

I'm pretty sure this exists, but I don't know what to search for:

I am refreshing content via JQuery's $('#somediv').load() and another via $.ajax(). I would like to catch situations where the new content is identical to the old content and slow开发者_如何学Go down the refresh rate.

I can imagine how to do it for the ajax case - but seems like I'd have to store in memory a lot of data.

But what about load?

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jQuery's load and $.ajax() functions only fetch once. If you are refreshing constantly, you must be using a timer or a loop. Just clear the timer and set a new interval.

var refreshRateMs = 5000;
timerId = setInterval("refreshPage()", refreshRateMs);

function refreshPage() {
  $("#somediv").load(); // Or other refresh code
}

// Later, you need to reduce the refresh rate (increase the interval):
clearInterval(timerId)
refreshRateMs += 1000; // Make delay 1s longer
timerId = setInterval("refreshPage()", refreshRateMs);

If you need to check using .load() that the new content is not identical to the old content before appending it, don't use .load(). .load() has an implicit callback function that will load it into the dom. Instead, use $.get:

$.get('page_to_load.html', function(data) {
   var newContent = $('.result').html(data);
   if newContent == $('.oldContent') { // Whatever check is necessary
       $("#somediv").append(newContent);
   }
});

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From a performance perspective, would I be right in assuming that the answer Jasie has provided requires that the browser load the entire remote file so that it can check the contents against the locally stored variable?

A more efficient method if you're looking for efficiency might be using ajax because it can just check the header and use the last modified date. (Stuff I read here http://www.ambitionlab.com/how-to-check-if-a-file-exists-using-jquery-2010-01-06)

Therefore a simple header check could be on repeat and then exit to a file reload only when modified date has changed.

I'm going to work on using this method and will post the results here when/if I get them working.