jsperf, test your function performance in browser

jsperf-local.js

;(function () {

    // * ---------------------------------------------------------------- tester

    var p = performance

    function loopTest(fn) {
        var count = 1
        var time = 0
        while (time < 100) {
            count *= 10
            time = loopTime(fn, count)
        }
        count = ~~(1000 / time * count)
        time = loopTime(fn, count)
        return (~~(1000 / time * count))
    }

    function loopTime(fn, n) {
        var time = p.now()
        while (n-- > 0) {
            fn()
        }
        return p.now() - time
    }

    // * ---------------------------------------------------------------- tool

    function toThousands(num) {
        return num.toString().replace(/(\d)(?=(\d{3})+$)/g, '$1,')
    }

    // * ---------------------------------------------------------------- exports

    window.jsperf = function (fnSet) {

        fnSet = (typeof fnSet == "function") ? {fn: fnSet} : fnSet
        var list = []

        // * Do an empty loop, because the first loop is super fast somehow
        console.log("starting...")
        loopTest(function () {})

        for (var label in fnSet) {
            var fn = fnSet[label]
            if (typeof fn == "function") {
                console.log("testing... " + label)
                var count = loopTest(fn)
                list.push({
                    "label": label,
                    "fn": "" + fn,
                    "ops/sec": count,
                    "ops/sec (thousands)": toThousands(count),
                })
            }
        }
        list = list.sort(function (a, b) {
            return b["ops/sec"] - a["ops/sec"]
        })
        var table = {}
        list.forEach(function (e) {
            table[e.label] = e
        })
        console.table(table, ["ops/sec (thousands)", "fn", "ops/sec"])

    }

    // * ---------------------------------------------------------------- 

})();

test

var set = {
    now1: performance.now.bind(performance),
    now2: () => performance.now(),
    now3: Date.now,
    now4: () => Date.now(),
}

jsperf(set)

jsperf(Date.now)