Throttle.js: rate limiter.

throttle.js

/**
 * Throttle function
 * 
 * Runs the `func` without any delay when called normally
 * but if called many times it will rate limit.
 */
function throttle (func, wait) {

    var t;
    var firstTime = true;

    return function () {
        var args = arguments;
        var othis = this;
        var didItRunAlready = false;

        if (firstTime) {
            func.apply(othis, args);
            didItRunAlready = true;
            firstTime = false;
        }
        clearTimeout(t);
        t = setTimeout(function () {
                if (!didItRunAlready) {
                    func.apply(othis, args);
                }
                firstTime = true;
            }, wait);
    }
}




/////////////// USAGE //////////////////

// example function
function showMessage(e) {
    console.log("showing message... ", Math.random());
    console.log("this ", this);
}

// html: <button id="btn">write something</button>

// usage
document.getElementById("btn").addEventListener("click", throttle(showMessage, 200));