gistfile1.js

(function($){
	var requests = {};

	$(function(){
		// Determine which data you need and call the getData()...
		// Stubbing in some example data...

		// This is a unique request and would make an ajax call
		getData({
			foo: 'bar'
		}, function(results){
			console.log('Results:', results);
		});

		// This is a unique request and would make an ajax call
		// Note the use of the returned promise
		getData({
			bar: 'foo'
		}).done(function(results){
			console.log('Results:', results);
		});

		// This is a duplicate request and would wait for the original call to finish
		getData({
			foo: 'bar'
		}, function(results){
			console.log('Results:', results);
		});

		// Above would have generated two AJAX requests...
	});

	function getData( query, callback ) {
		query = query || {};

		// Create a repeatable, unique key for the request
		hash = MD5( JSON.stringify(query) );

		if(!requests[hash]) {
			requests[ hash ] = $.getJSON( "/some/path", query ).promise();
                        // Or if you only want results and no ajax thingy
                        // requests[ hash ] = $.getJSON( "/some/path", query ).pipe(function( results ) { return results; });
		}

		return requests[hash].done( callback );
	}
})(jQuery);