JSFiddle - React, Tailwind, and code Playground

HTML

<p>if else <span id="if">.</span>ms</p>
<p>switch <span id="sw">.</span>ms</p>
<p><span id="speed">.</span>
</p>

JavaScript

var tNone, t1to4, t5to8, t9to11, i, max = 10000000,
    start, d, x, tIf, tSw;

tNone = 0;
t1to4 = 0;
t5to8 = 0;
t9to11 = 0;

start = new Date().getTime();
for (i = 0; i < max; i++) {
    d = Math.floor(Math.random() * 13);
    if (1 <= d && d <= 11) {
        if (d <= 4) {
            t1to4++;
        } else if (d <= 8) {
            t5to8++;
        } else {
            t9to11++;
        }
    } else {
        tNone++;
    }
}
tIf = new Date().getTime() - start;
$("#if").text(tIf);

start = new Date().getTime();
for (i = 0; i < max; i++) {
    x = Math.floor(Math.random() * 13);
    switch (true) {
        case (x >= 1 && x < 5):
            t1to4++;
            break;
        case (x > 4 && x < 9):
            t5to8++;
            break;
        case (x > 8 && x < 12):
            t9to11++;
            break;
        default:
            tNone++;
            break;
    }
}
tSw = new Date().getTime() - start;
$("#sw").text(tSw);

if (tSw > tIf) {
    var p = Math.round((tSw / tIf - 1) * 100);
    $("#speed").text("switch takes " + p + "% more time than if");
} else {
    var p = Math.round((tIf / tSw - 1) * 100);
    $("#speed").text("if takes " + p + "% more time than switch");
}