Underscore filter over large dataset

HTML

<script src="https://cdnjs.cloudflare.com/ajax/libs/underscore.js/1.8.3/underscore-min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.1.1/jquery.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/mathjs/3.10.0/math.min.js"></script>
<div>
	<span id="done"></span>
</div>

JavaScript

var cars = [];
var size = 5000;

addText("started");

for (var i=0;i<size;i++){
	var randomBool = Math.random() >= 0.5;
	cars.push({name: "car_name_"+i, operation: i, selected: randomBool});
}
addText("added: " + cars.length + " elements");

//capture console timings
console.time("filtering");

var filteredCars = _.where(cars, {selected: true});
addText("filtered to: " + filteredCars.length + " checked/selected elements");

var operations = _.map(filteredCars, function(car){ return {id: car.operation};});

//output to console time taken to filter out elements of cars array
console.timeEnd("filtering");

var jsonResult = JSON.stringify(operations);
addText("JSON length: " + jsonResult.length);
addText("-------------------------");
addText("JSON: " + jsonResult);


function addText(s) {
    $("#done").append("<div>" + s + "</div>");
}