Convert function to throttle function

throttleFn.js

function throttleFn(fn, wait, context) {
    wait = wait || defaultThrottleWait;
    var last, timeoutId;

    return function() {
        var ctx = (context || this),
            now = +new Date,
            args = arguments;

        if (last && now < (last + wait)) {
            clearTimeout(timeoutId);
            timeoutId = setTimeout(function() {
                last = now;
            }, wait);
        } else {
            last = now;
            fn.apply(ctx, args);
        }
    };
}