Autocomplete javascript de um texto via ajax com delay

busca.js

	var oldValor = "";
	var xhr;

	function trata(data) {
	    //var json = JSON.parse(data);
	    console.log("tratando....");
	    var options = $("#options");
	    $(options).empty();
	    var json = data;
	    
	    $.each(json, function(i, item) {
	        var obj = json[i];
	        $(options).append("<li>" + obj.nome + "</li>");
	    });
	};

	$(function(){
		var oldValor = "";
		
		$('#searchString').keyup(function(e) {
		    clearTimeout($.data(this, 'timer'));
		    if (e.keyCode == 13)
		      search(true);
		    else
		      $(this).data('timer', setTimeout(search, 300));
		});
		function search(force) {
		    var existingString = $("#searchString").val();
		    
		    if (existingString == oldValor) {
		    	return; 
		    }
		    
		    oldValor = existingString;

		    console.log("search. force = "+force+". texto = "+existingString);

		    //if (!force){ return; }

		    //GET
		    /*
		    $.get('/consulta/busca?valor=' + existingString, function(data) {
		        console.log("foi");
		        trata(data);
		    });
		    */
		    
		    //POST
		    var limite = 15;
		    $.ajax({ 
				url: '/consulta/buscaPost',
			    type: 'POST',
			    data: {valor : existingString, limite: limite},
			    success: function(data) {
			       trata(data);
			    }
			});		    
		}		
		
	});