Test functions to show that accessing Math as a global is much slower than if it were local.

global-access.js

function f1(N) {
    var i, sum = 0;
    for (i = 0; i < N; ++i) {
        sum += Math.sin(i);
    }
    return sum;
}

function f2(f) {
    return function (N) {
        var i, sum = 0;
        for (i = 0; i < N; ++i) {
            sum += f(i);
        }
        return sum;
    };
}

function f3(Module) {
    return function (N) {
        var i, sum = 0;
        for (i = 0; i < N; ++i) {
            sum += Module.sin(i);
        }
        return sum;
    };
}

// f(N) is run a few times, timed and some stats are
// returned as an object.
function timeit(f, N) {
    var start, stop, dt;
    var worst = 0, best = 1000 * 3600, mean = 0, sigma = 0;
    var i, M = 7;
    for (i = 0; i < M; ++i) {
        start = Date.now();
        f(N);
        stop = Date.now();
        dt = stop - start;
        best = Math.min(best, dt);
        worst = Math.max(worst, dt);
        mean += dt;
        sigma += dt * dt;
    }

    mean /= M;
    sigma /= M;

    return { best: best, worst: worst, mean: mean, spread: Math.sqrt(sigma - mean * mean) };
}

Macbook Air 1.7GHz Core i5 / 4GB / Lion
N = 100M and reporting only 2 significant figures

Chrome [15.0.849.1 dev]: f1local = 23 secs, f2local = 13 secs
Safari [5.1 (7534.48.3)]: f1local = 8.6 secs, f2local = 8.6 secs
Firefox [6.0]: f1local = 13 secs, f2local = 12 secs

Intel(R) Core(TM)2 Quad CPU Q6600 @ 2.40GHz 4GB RAM Windows Vista

N = 100M; 23 sec in FF 6.0.2 (f1local)
N = 100M; 17 sec in FF 6.0.2 (f2local)

N = 100M; 28 sec in Safari 5.1 (7534.50) (f1local)
N = 100M; 13 sec in Safari 5.1 (7534.50) (f2local)

N = 100M; 45 sec in Chrome 14.0.835.163 beta-m (f1local)
N = 100M; 15 sec in Chrome 14.0.835.163 beta-m (f2local)

(Thanks Bharat!)