Initial commit

Utility/setTimer.js

@@ -0,0 +1,131 @@
+(function(w) {
+    
+    /**
+    *   The main constructor function.
+    *   @constructor
+    *   @param {Function} onTick The tick function.
+    *   @param {Number} interval The tick duration.
+    *   @returns {Timer} The instance of timer.
+    */
+    var Timer = function(onTick, interval) {
+        this.setInterval(interval);
+        this.setOnTick(onTick);
+        
+        this._timer = null;
+        this._active = false;
+        
+        this._startTime = 0;
+    };
+    
+    
+    /**
+    *   Start the timer.
+    *   The tick function is called with one argument, the drift amount (int).
+    *   @returns {Timer} this.
+    */
+    Timer.prototype.start = function() {
+        
+        let drift = 0,
+            actual = 0,
+            ideal = 0,
+            counter = 0,
+            time = 0,
+            that = this,
+            now = performance.now;
+        
+        
+        function onTick() {
+            that._onTick(drift);
+            
+            ++counter;
+            
+            ideal = that._interval * counter;
+            actual = now() - that._startTime;
+            drift = actual - ideal;
+            time = that._interval - drift;
+
+            
+            
+            if (that._active) setTimeout(onTick, time);
+        }
+        
+        that._active = true;
+        that._startTime = now();
+        that._timer = setTimeout(onTick, that._interval);
+        
+        return this;
+    };
+    
+    
+    /**
+    *   Stop the timer.
+    *   @returns {Timer} this.
+    */
+    Timer.prototype.stop = function() {
+        this._active = false;
+        clearTimeout(this._timer);
+        return this;
+    };
+    
+    
+    /**
+    *   Set the tick duration. Can be called whilst timer is running.
+    *   @param {Number} ms The tick duration.
+    *   @returns {Timer} this.
+    */
+    Timer.prototype.setInterval = function(ms) {
+        if(isNaN(ms)) {
+            throw new Error('Timer.setInterval requires a number');
+        }
+        else if(ms < 10) {
+            ms = 10;
+        }
+        
+        this._interval = ms;
+        return this;
+    };
+    
+    /**
+    *   Allow for replacement of the tick function, even whilst the timer
+    *   is running.
+    *   @param {Function} onTick The new tick function to be called on each cycle.
+    *   @returns {Timer} this.
+    */
+    Timer.prototype.setOnTick = function(onTick) {
+        this._onTick = onTick;
+        return this;
+    };
+    
+    
+    
+    /**
+    *   Allow the `Timer` constructor to be used as a replacement for 
+    *   setInterval.
+    *   @param {Function} tick The tick function to call every `interval` ms.
+    *   @param {Number} interval The tick duration.
+    *   @returns {Timer} A new instance of the `Timer` constructor.
+    */
+    var setTimer = function(tick, interval) {
+        var timer = new Timer(tick, interval);
+        timer.start();
+        return timer;
+    };
+    
+    
+    /**
+    *   Imitate the clearTimeout method...
+    *   @param {Timer} 
+    */
+    var clearTimer = function(timer) {
+        timer.stop();
+    };
+    
+    
+    
+    w.Timer = Timer;
+    w.setTimer = setTimer;
+
+
+
+
+}(global));