press-ui/mixins/scroller/scroll.js

简单、易用的跨端组件库，兼容 Vue2 和 Vue3，同时支持 uni-app和普通 Vue 项目

import { Friction } from './friction';
import { Spring } from './spring';

export function Scroll(extent, friction, spring) {
  this._extent = extent;
  this._friction = friction || new Friction(0.01);
  this._spring = spring || new Spring(1, 90, 20);
  this._startTime = 0;
  this._springing = false;
  this._springOffset = 0;
}

Scroll.prototype.snap = function (e, t) {
  this._springOffset = 0;
  this._springing = true;
  this._spring.snap(e);
  this._spring.setEnd(t);
};
Scroll.prototype.set = function (e, t) {
  this._friction.set(e, t);
  if (e > 0 && t >= 0) {
    this._springOffset = 0;
    this._springing = true;
    this._spring.snap(e);
    this._spring.setEnd(0);
  } else {
    if (e < -this._extent && t <= 0) {
      this._springOffset = 0;
      this._springing = true;
      this._spring.snap(e);
      this._spring.setEnd(-this._extent);
    } else {
      this._springing = false;
    }
  }
  this._startTime = (new Date()).getTime();
};
Scroll.prototype.x = function (e) {
  if (!this._startTime) {
    return 0;
  }
  if (!e) {
    e = ((new Date()).getTime() - this._startTime) / 1e3;
  }
  if (this._springing) {
    return this._spring.x() + this._springOffset;
  }
  let t = this._friction.x(e);
  const n = this.dx(e);
  if ((t > 0 && n >= 0) || (t < -this._extent && n <= 0)) {
    this._springing = true;
    this._spring.setEnd(0, n);
    if (t < -this._extent) {
      this._springOffset = -this._extent;
    } else {
      this._springOffset = 0;
    }
    t = this._spring.x() + this._springOffset;
  }
  return t;
};
Scroll.prototype.dx = function (e) {
  let t = 0;
  t = this._lastTime === e ? this._lastDx : this._springing ? this._spring.dx(e) : this._friction.dx(e);
  this._lastTime = e;
  this._lastDx = t;
  return t;
};
Scroll.prototype.done = function () {
  return this._springing ? this._spring.done() : this._friction.done();
};
Scroll.prototype.setVelocityByEnd = function (e) {
  this._friction.setVelocityByEnd(e);
};
Scroll.prototype.configuration = function () {
  const e = this._friction.configuration();
  e.push.apply(e, this._spring.configuration());
  return e;
};