weex-nuke/lib/node_modules/nuke-web-picker/src/view/animate.js

基于 Rax 、Weex 的高性能组件体系 ~~

'use strict';

let counter = 1;
const running = {};

export const Animate = {

  requestAnimationFrame: (() => {
    // isomorphic support
    if (typeof window === 'undefined') {
      return () => { };
    }

    const requestFrame = window.requestAnimationFrame || window.webkitRequestAnimationFrame;

    return (callback) => {
      requestFrame(callback);
    };
  })(),

  start(stepFunc, callback, duration, easeFunc) {
    const { max, min } = Math;
    const animateId = counter++;

    let startTime = null, lastTime = null;

    running[animateId] = true;

    const step = (timeStamp) => {
      if (running[animateId] !== true) {
        return;
      }

      if (startTime === null) {
        startTime = timeStamp;
        lastTime = timeStamp;
      }

      let percent = 0,
        timeDiff = timeStamp - startTime,
        timeFrame = timeStamp - lastTime;

      lastTime = timeStamp;

      if (duration) {
        percent = min(timeDiff / duration, 1);
      }

      if (percent >= 1 || running[animateId] !== true) {
        stepFunc(percent, timeDiff, timeFrame);
        callback();

        running[animateId] = false;
        delete running[animateId];
        return;
      }

      if (easeFunc) {
        percent = easeFunc(timeDiff, 0, 1, duration);
      }

      stepFunc(percent, timeDiff, timeFrame);

      Animate.requestAnimationFrame(step);
    };

    Animate.requestAnimationFrame(step);

    return animateId;
  },

  stop(animateId) {
    running[animateId] = false;
    delete running[animateId];
  }
}

export function easeOutBounce(t, b, c, d) {
  if ((t /= d) < (1 / 2.75)) {
    return c * (7.5625 * t * t) + b;
  } else if (t < (2 / 2.75)) {
    return c * (7.5625 * (t -= (1.5 / 2.75)) * t + .75) + b;
  } else if (t < (2.5 / 2.75)) {
    return c * (7.5625 * (t -= (2.25 / 2.75)) * t + .9375) + b;
  } else {
    return c * (7.5625 * (t -= (2.625 / 2.75)) * t + .984375) + b;
  }
}


export function easeInOutQuad(t, b, c, d) {
  if ((t /= d / 2) < 1) return c / 2 * t * t + b;
  return - c / 2 * ((--t) * (t - 2) - 1) + b;
}