Testing performance of difference ways of appending to a new array.

concatTest.js

'use strict';
var iterations = 1000000,
    outerIterations = 100;

function runit() {
    var ary
        ,result
        ,idx;
    ary = createData();
    console.log('Executing while loop with prefix incre in test condition');
    result = executeOuterLoop(pushForLoop, ary);
    printResult(result);
    console.log('Concatenating using concat');
    result = executeOuterLoop(concat, ary);
    printResult(result);
    console.log('Concatenating using push with the forEach function');
    result = executeOuterLoop(forEachFunc, ary);
    printResult(result);
}

function executeOuterLoop(loopFunc, ary) {
    var idx,
        sum = [0, 0],
        result;
    for (idx = 0; idx < outerIterations; idx++) {
        result = loopFunc(ary.slice(0));
        sum[0] += result[0];
        sum[1] += result[1];
    }
    sum[0] = sum[0] / outerIterations;
    sum[1] = sum[1] / outerIterations;
    return sum;
}

function printResult(diff) {
    console.log('Loop time was %d seconds and %d milliseconds', diff[0], diff[1] / 1000000);
}

function createData() {
    var idx
        ,retVal = [];
    for (idx = 0 ; idx < iterations; idx++) {
        retVal.push(Math.floor((Math.random() * 10) + 1));
    }
    return retVal;
}

function pushForLoop(ary) {
    var start
        ,diff
        ,idx
		,addTo = [];
    start = process.hrtime();
    for (idx = 0; idx < ary.length; idx++) {
        addTo.push(ary[idx]);
    }
    diff = process.hrtime(start);
    return diff;
}

function concat(ary) {
    var start
        ,diff
        ,idx
		,addTo = [];
    start = process.hrtime();
	addTo.concat(ary);
    diff = process.hrtime(start);
    return diff;
}

function forEachFunc(ary) {
	var start
        ,diff
        ,idx
		,addTo = [];
    start = process.hrtime();
    idx = -1;
	ary.forEach(function (val) {
		addTo.push(val);
	});
   
    diff = process.hrtime(start);
    return diff;
}

runit();