joinTest.js

Array.prototype.myJoin = function(aDelemiter)
{
    if (aDelemiter === null)
        aDelemiter = ",";

    if (this.length > 0)
    var str = this[0];

    for (var i = 1; i < this.length; i++) {
        str += aDelemiter + this[i];
    }

    return str;
}



function runTest(objcCount, aDelemiter)
{
    var manualTotal = 0;
    var autoTotal = 0;

    var builtInTime = 0;
    var manualTime  = 0;
    var objs = [];

    //console.log("populating array");
    for (var i = 0; i < objcCount; i++) {
        objs[i] = String(i);
    };

    for (var i = 0; i < 4; i++)
    {

        var start = new Date();
        var out = objs.join(aDelemiter);
        var end = new Date();

        builtInTime = end - start;

        var start2 = new Date();
        var out = objs.myJoin("");
        var end2 = new Date();

        manualTime = end2 - start2;

        console.log("Test " + i + ": ");
        console.log("     Manual Time:   " + manualTime / 1000 + "s");
        console.log("     Built In Time: " + builtInTime / 1000 + "s");
        manualTotal += manualTime;
        autoTotal += builtInTime;
    }

    console.log("Average of " + objcCount + " objects:");
    console.log("Manual Time:   " + manualTotal / 4000 + "s");
    console.log("Built In Time: " + autoTotal / 4000 + "s");

    if (manualTotal < autoTotal)
            console.log("Manual join is faster");
    else if (autoTotal < manualTotal)
            console.log("Built in join is faster");
    else
        console.log("Built in and manual joins are the same");

    console.log("----------------------------------------");
    console.log("----------------------------------------");
}
runTest(  10000, "");
runTest( 250000, "");
runTest( 500000, "");
runTest(1000000, "");
runTest(2000000, "");
runTest(3000000, "");
runTest(4000000, "");

Results.txt

Test 0: 
     Manual Time:   0.001s
     Built In Time: 0s
Test 1: 
     Manual Time:   0s
     Built In Time: 0s
Test 2: 
     Manual Time:   0.003s
     Built In Time: 0s
Test 3: 
     Manual Time:   0s
     Built In Time: 0s
Average of 10000 objects:
Manual Time:   0.001s
Built In Time: 0s
Built in join is faster
----------------------------------------
----------------------------------------
Test 0: 
     Manual Time:   0.033s
     Built In Time: 0.066s
Test 1: 
     Manual Time:   0.008s
     Built In Time: 0.079s
Test 2: 
     Manual Time:   0.029s
     Built In Time: 0.044s
Test 3: 
     Manual Time:   0.007s
     Built In Time: 0.066s
Average of 250000 objects:
Manual Time:   0.01925s
Built In Time: 0.06375s
Manual join is faster
----------------------------------------
----------------------------------------
Test 0: 
     Manual Time:   0.057s
     Built In Time: 0.093s
Test 1: 
     Manual Time:   0.09s
     Built In Time: 0.07s
Test 2: 
     Manual Time:   0.061s
     Built In Time: 0.061s
Test 3: 
     Manual Time:   0.101s
     Built In Time: 0.064s
Average of 500000 objects:
Manual Time:   0.07725s
Built In Time: 0.072s
Built in join is faster
----------------------------------------
----------------------------------------
Test 0: 
     Manual Time:   0.134s
     Built In Time: 0.242s
Test 1: 
     Manual Time:   0.218s
     Built In Time: 0.2s
Test 2: 
     Manual Time:   0.174s
     Built In Time: 0.199s
Test 3: 
     Manual Time:   0.209s
     Built In Time: 0.233s
Average of 1000000 objects:
Manual Time:   0.18375s
Built In Time: 0.2185s
Manual join is faster
----------------------------------------
----------------------------------------
Test 0: 
     Manual Time:   0.327s
     Built In Time: 0.308s
Test 1: 
     Manual Time:   0.393s
     Built In Time: 0.277s
Test 2: 
     Manual Time:   0.307s
     Built In Time: 0.283s
Test 3: 
     Manual Time:   0.412s
     Built In Time: 0.284s
Average of 2000000 objects:
Manual Time:   0.35975s
Built In Time: 0.288s
Built in join is faster
----------------------------------------
----------------------------------------
Test 0: 
     Manual Time:   0.602s
     Built In Time: 0.355s
Test 1: 
     Manual Time:   0.497s
     Built In Time: 0.363s
Test 2: 
     Manual Time:   0.464s
     Built In Time: 0.365s
Test 3: 
     Manual Time:   0.66s
     Built In Time: 0.359s
Average of 3000000 objects:
Manual Time:   0.55575s
Built In Time: 0.3605s
Built in join is faster
----------------------------------------
----------------------------------------
Test 0: 
     Manual Time:   0.799s
     Built In Time: 0.865s
Test 1: 
     Manual Time:   0.61s
     Built In Time: 0.928s
Test 2: 
     Manual Time:   0.864s
     Built In Time: 0.86s
Test 3: 
     Manual Time:   0.645s
     Built In Time: 0.886s
Average of 4000000 objects:
Manual Time:   0.7295s
Built In Time: 0.88475s
Manual join is faster