How to mimic a shake animation effect using pure javascript

I create a function that when mouseover trigger a shake animation. Now I need to make sure it shakes for ever after the mouseover. Thank you guys.

function shake(e, oncomplete, distance, time) {
    var time = 500;
    var distance = 5;

    var start = (new Date()).getTime();
    animate();

    function animate() {
        var now = (new Date()).getTime();
        // Get current time
        var elapsed = now - start;
        // How long since we started
        var fraction = elapsed / time;
        // What fraction of total time?
        if (fraction < 1) {
            var x = distance * Math.sin(fraction * 4 * Math.PI);
            e.style.left = x + "px";
            // We're aiming for a smooth 40 frames/second animation.
            setTimeout(animate, Math.min(25, time - elapsed));
        } else {
            // Otherwise, the animation is complete
            if (oncomplete) oncomplete(e);
            // Invoke completion callback
        }
    }
}

function shakeme(event1) {
    shake(event1.target);
}

document.getElementById("wood").addEventListener("mouseover", shakeme, false);

<button id="wood">Hello World</button>