Performance test: Loops versus array methods

perftest.js

// This script should be run with Node.js

var short = generateDummy(100);
var med = generateDummy(10000);
var long = generateDummy(1000000);

console.info('Big loop:');
test(short, bigLoop);
test(med, bigLoop);
test(long, bigLoop);
console.info('Array methods:');
test(short, arrayMethods);
test(med, bigLoop);
test(long, arrayMethods);

function test(data, fn) {
    var hrstart = process.hrtime();
    fn(data);
    var hrend = process.hrtime(hrstart);
    console.info(data.length+",%d", hrend[1]/1000000);
}

function generateDummy(length) {
    var dummy = [];
    for (var i = 0; i < length; i++) {
        dummy.push({
            seats: Math.round(Math.random() * 100),
            visible: (Math.random() < 0.2)
        });
    }
    return dummy;
}

function bigLoop(data) {
    var seats = 0;
    var processed = [];
    var filtered = [];
    for (var i = 0; i < data.length; i++) {
        var d = data[i];
        d.seatsPc = (d.seats / 320) * 100;
        processed.push(d);
        seats += d.seats;
        if (d.visible === true) {
            filtered.push(d);
        }
    }
}

function arrayMethods(data) {
    // calculate percentages for each item
    var processed = data.map(function(d,i) {
        d.seatsPc = (d.seats / 320) * 100;
        return d;
    });
    // count total seats
    var seats = data.map(function(d,i) {
        return d.seats;
    }).reduce(function(prev,curr) {
        return prev + curr;
    });
    // create new filtered array
    var filtered = data.filter(function(d,i) {
        return d.visible;
    });
}