Edit in JSFiddle

function debounce(func, wait, immediate) {
    var timeout;
    return function() {
        var context = this,
            args = arguments;
        var later = function() {
            timeout = null;
            if (!immediate) func.apply(context, args);
        };
        var callNow = immediate && !timeout;
        clearTimeout(timeout);
        timeout = setTimeout(later, wait);
        if (callNow) func.apply(context, args);
    };
};

var logging = debounce(function(){
    alert("Heavy task");
}, 5000);

<button onclick="setTimeout(logging, 100);">Execute Function After 100ms</button>