<button id="button">click</button>

(function(window, document, undefined){
    'use strict';
    var start;
    var end;
    var delta;
    var button = document.getElementById("button");

    button.addEventListener("mousedown", function(){
        start = new Date();
    });

    button.addEventListener("mouseup", function() {
        end = new Date();
        delta = end - start;
        if (delta > 0 && delta < 500) {
            alert("less than half second:");
        }
        if (delta > 1000) {
            alert("more than a second:");
        }
    });
})(window, document);

var start,
    end,
    delta,
    button = document.getElementById('button');