Call function at most once per every [wait] milliseconds. Useful for rate-limiting.

func.throttle.js

window.addEventListener('resize', throttle(resizer, 200));        

function throttle(func, wait) {
    // from underscore.js
    var _now = Date.now || function() { return new Date().getTime(); },
        context, args, result, timeout = null, previous = 0;
    var later = function() {
        previous = _now();
        timeout = null;
        result = func.apply(context, args);
        if (!timeout) context = args = null;
    };
    return function() {
        var now = _now(), remaining = wait - (now - previous);
        context = this;
        args = arguments;
        if (remaining <= 0 || remaining > wait) {
            if (timeout) {
                clearTimeout(timeout);
                timeout = null;
            }
            previous = now;
            result = func.apply(context, args);
            if (!timeout) context = args = null;
        } else if (!timeout && options.trailing !== false) {
            timeout = setTimeout(later, remaining);
        }
        return result;
    };
}