tapper.js

/**
 * Tapper
 * tap, step, tap, roll, roll, roll ...
 * @see http://d.hatena.ne.jp/brazil/20071030/1193711816
 */
function Tapper() {
    this.rolling = false;
    this.unbounded = false;
    this.tapped = 0;
    this.lastTapped = 0;
    this.interval = 0;
    this.previous = null;
    this.defalutGap = 60;
    this.minInterval = 16;
    this.maxInterval = 3000;
}
(function(member) { member.apply(Tapper.prototype); })(function() {
    // method
    this. tap =  tap;  // tick down a interval between tap and tap. (ex: tapper.tap(e.keyCode); //when keydown.)
    this.step = step;  // call between taps to separate taps.       (ex: tapper.step();         //when keyup.  )
    this. gap =  gap;  // returns adjusted interval.
    this.roll = roll;  // repeat given function at a regular interval which returned the gap method.
    this.stop = stop;  // stop rolling.
    // impl
    function tap(value) {
        if (!this.unbounded) {
            this.unbounded = true;
            var now = new Date().getTime();
            if (this.previous == value) {
                this.tapped++;
                if (this.tapped >= 2) {
                    this.interval = now - this.lastTapped;
                }
            }
            else {
                this.previous = value;
                this.interval = -1;
                this.tapped = 1;
            }
            this.lastTapped = now;
        }
        else {
            if (this.previous != value) { // left tap, right tap (no step).
                this.stop();
            }
        }
    }
    function step() {
        this.stop();
        this.unbounded = false;
    }
    function gap(interval) {
        return (interval < 1000) ? Math.max(16, Math.floor(interval + ((interval - 500) * 0.2))) : (interval + 100);
    }
    function roll(func) {
        this.stop();
        this.rolling = true;
        var ivl = this.interval;
        var fromLastTapped = new Date().getTime() - this.lastTapped;
        var gap, firstRoll;
        if (ivl <= 0 || ivl <= this.minInterval || ivl >= this.maxInterval) {
            gap = this.defalutGap;
            firstRoll = (fromLastTapped >= gap) ? 0 : (gap - fromLastTapped);
        }
        else {
            gap = this.gap(ivl);
            firstRoll = (fromLastTapped >= ivl) ? 0 : (ivl - fromLastTapped);
        }
        var self = this;
        this.rollingTid = setInterval(function() {
            func();
            if (self.rollingTid) {
                clearInterval(self.rollingTid);
                self.rollingTid = setInterval(func, gap);
            }
        }, firstRoll);
        this.interval = -1;
        this.tapped = 0;
    }
    function stop() {
        this.rolling = false;
        if (this.rollingTid) {
            clearInterval(this.rollingTid);
            this.rollingTid = null;
        }
    }
});