原生JS实现全屏滚动插件：原理、代码与性能优化

/**
 * 全屏滚动类
 */
class PureFullPage {
 // 构造函数
 constructor() {}

 // 原型方法
 methods() {}

 // 初始化函数
 init() {}
}

<body>
 <div id="pureFullPageContainer">
  <div class="page"></div>
  <div class="page"></div>
  <div class="page"></div>
 </div>
</body>

body {
 /* body 为容器直接的父元素 */
 overflow: hidden;
}

#pureFullPage {
 /* 只有当 position 的值不是 static 时，top 值才有效 */
 position: relative;
 /* 设置初始值 */
 top: 0;
}
.page {
 /* 此处不能为 100vh，后面详述 */
 /* 其父元素，也就是 #pureFullPage 的高度，通过 js 动态设置*/
 height: 100%;
}

// 伪代码
'#pureFullPage'.style.height = document.documentElement.clientHeight + 'px';

// 鼠标滚轮事件
getWheelDelta(event) {
 if (event.wheelDelta) {
  return event.wheelDelta;
 } else {
  // 兼容火狐
  return -event.detail;
 }
},

// 鼠标滚动逻辑（全屏滚动关键逻辑）
scrollMouse(event) {
 let delta = utils.getWheelDelta(event);
 // delta < 0，鼠标往前滚动，页面向下滚动
 if (delta < 0) {
  this.goDown();
 } else {
  this.goUp();
 }
}

goUp() {
 // 只有页面顶部还有页面时页面向上滚动
 if (-this.container.offsetTop >= this.viewHeight) {
  // 重新指定当前页面距视图顶部的距离 currentPosition，实现全屏滚动，
  // currentPosition 为负值，越大表示超出顶部部分越少
  this.currentPosition = this.currentPosition + this.viewHeight;

  this.turnPage(this.currentPosition);
 }
}
goDown() {
 // 只有页面底部还有页面时页面向下滚动
 if (-this.container.offsetTop <= this.viewHeight * (this.pagesNum - 2)) {
  // 重新指定当前页面距视图顶部的距离 currentPosition，实现全屏滚动，
  // currentPosition 为负值，越小表示超出顶部部分越多
  this.currentPosition = this.currentPosition - this.viewHeight;

  this.turnPage(this.currentPosition);
 }
}

// 鼠标滚轮监听，火狐鼠标滚动事件不同其他
if (navigator.userAgent.toLowerCase().indexOf('firefox') === -1) {
 document.addEventListener('mousewheel', scrollMouse);
} else {
 document.addEventListener('DOMMouseScroll', scrollMouse);
}

// 手指接触屏幕
document.addEventListener('touchstart', event => {
 this.startY = event.touches[0].pageY;
});
//手指离开屏幕
document.addEventListener('touchend', event => {
 let endY = event.changedTouches[0].pageY;
 if (endY - this.startY < 0) {
  // 手指向上滑动，对应页面向下滚动
  this.goDown();
 } else {
  // 手指向下滑动，对应页面向上滚动
  this.goUp();
 }
});

// 阻止 touchmove 下拉刷新
document.addEventListener('touchmove', event => {
 event.preventDefault();
});

// 防抖动函数，method 回调函数，context 上下文，event 传入的时间，delay 延迟函数
debounce(method, context, event, delay) {
 clearTimeout(method.tId);
 method.tId = setTimeout(() => {
  method.call(context, event);
 }, delay);
},

// 截流函数，method 回调函数，context 上下文，delay 延迟函数，
// immediate 传入 true 表示在 delay 开始时执行回调函数
throttle(method, context, delay, immediate) {
 return function() {
  const args = arguments;
  const later = () => {
   method.tID = null;
   if (!immediate) {
    method.apply(context, args);
   }
  };
  const callNow = immediate && !method.tID;
  clearTimeout(method.tID);
  method.tID = setTimeout(later, delay);
  if (callNow) {
   method.apply(context, args);
  }
 };
},

// 设置截流函数
let handleMouseWheel = utils.throttle(this.scrollMouse, this, this.DELAY, true);

// 鼠标滚轮监听，火狐鼠标滚动事件不同其他
if (navigator.userAgent.toLowerCase().indexOf('firefox') === -1) {
 document.addEventListener('mousewheel', handleMouseWheel);
} else {
 document.addEventListener('DOMMouseScroll', handleMouseWheel);
}

// 创建右侧点式导航
createNav() {
 const nav = document.createElement('div');
 nav.className = 'nav';
 this.container.appendChild(nav);
 // 有几页，显示几个点
 for (let i = 0; i < this.pagesNum; i++) {
  nav.innerHTML += '<p class="nav-dot"><span></span></p>';
 }
 const navDots = document.querySelectorAll('.nav-dot');
 this.navDots = Array.prototype.slice.call(navDots);
 // 添加初始样式
 this.navDots[0].classList.add('active');
 // 添加点式导航点击事件
 this.navDots.forEach((el, i) => {
  el.addEventListener('click', event => {
   // 页面跳转
   this.currentPosition = -(i * this.viewHeight);
   this.turnPage(this.currentPosition);
   // 更改样式
   this.navDots.forEach(el => {
    utils.deleteClassName(el, 'active');
   });
   event.target.classList.add('active');
  });
 });
}

constructor(options) {
 // 默认配置
 const defaultOptions = {
  isShowNav: true,
  delay: 150,
  definePages: () => {},
 };
 // 合并自定义配置
 this.options = Object.assign(defaultOptions, options);
}

// window resize 时重新获取位置
getNewPosition() {
 this.viewHeight = document.documentElement.clientHeight;
 this.container.style.height = this.viewHeight + 'px';
 let activeNavIndex;
 this.navDots.forEach((e, i) => {
  if (e.classList.contains('active')) {
   activeNavIndex = i;
  }
 });
 this.currentPosition = -(activeNavIndex * this.viewHeight);
 this.turnPage(this.currentPosition);
}

handleWindowResize(event) {
 // 设置防抖动函数
 utils.debounce(this.getNewPosition, this, event, this.DELAY);
}

// 窗口尺寸变化时重置位置
window.addEventListener('resize', this.handleWindowResize.bind(this));

// polyfill Object.assign
polyfill() {
 if (typeof Object.assign != 'function') {
  Object.defineProperty(Object, 'assign', {
   value: function assign(target, varArgs) {
    if (target == null) {
     throw new TypeError('Cannot convert undefined or null to object');
    }
    let to = Object(target);
    for (let index = 1; index < arguments.length; index++) {
     let nextSource = arguments[index];
     if (nextSource != null) {
      for (let nextKey in nextSource) {
       if (Object.prototype.hasOwnProperty.call(nextSource, nextKey)) {
        to[nextKey] = nextSource[nextKey];
       }
      }
     }
    }
    return to;
   },
   writable: true,
   configurable: true,
  });
 }
},

getWheelDelta(event) {
 if (event.wheelDelta) {
  // 第一次调用之后惰性载入，无需再做检测
  this.getWheelDelta = event => event.wheelDelta;
  // 第一次调用使用
  return event.wheelDelta;
 } else {
  // 兼容火狐
  this.getWheelDelta = event => -event.detail;
  return -event.detail;
 }
},