Method constructor

plugins/tweenSystem.js:51–91

Create a new tween. The callback fires immediately with `start` so the * target snaps to the start value on the same frame the tween is created. * * `start` and `end` may be numbers, Vector2 instances, Color instances, or * any object exposing a `lerp(other, percent) => sameTy

(callback, start = 0, end = 1, duration = 1, options = {})

     *  @param {boolean} [options.useRealTime=false] - Advance even when the game is paused (matches Timer's useRealTime)
     *  @param {boolean} [options.paused=false] - Start in paused state */
    constructor(callback, start = 0, end = 1, duration = 1, options = {})
    {
        ASSERT(typeof callback === 'function', 'Tween callback must be a function');
        if (isLerpable(start))
        {
            ASSERT(start.constructor === end.constructor,
                'Tween start and end must be the same type');
        }
        else
        {
            ASSERT(isNumber(start), 'Tween start must be a number or have a .lerp method');
            ASSERT(isNumber(end),   'Tween end must be a number when start is a number');
        }
        ASSERT(isNumber(duration) && duration > 0, 'Tween duration must be > 0');

        /** @property {function(number|Vector2|Color):void} - Called with the interpolated value each frame */
        this.callback = callback;
        /** @property {number|Vector2|Color} - Starting value */
        this.start = start;
        /** @property {number|Vector2|Color} - Ending value */
        this.end = end;
        /** @property {number} - Total duration in seconds */
        this.duration = duration;
        /** @property {number} - Remaining time in seconds (counts down from duration to 0) */
        this.life = duration;
        /** @property {function(number):number} - Easing curve mapping [0,1] -> [0,1] */
        this.ease = options.ease || Ease.LINEAR;
        /** @property {boolean} - If true, advance even when the game is paused */
        this.useRealTime = !!options.useRealTime;
        /** @property {boolean} - If true, stop advancing until cleared */
        this.paused = !!options.paused;

        /** @private completion callback set by then(), loop(), pingPong(). */
        this.thenCallback = undefined;
        /** @private remaining iterations including the current run (loop/pingPong only). */
        this.loopRemaining = 0;

        tweenActive.push(this);
        // Snap target to start immediately.
        callback(this.interp(duration));
    }

    /** Set the easing curve and return this for chaining.
     *  @param {function(number):number} easeFn