function calculateExponent(base,exponent){
    if(exponent == 1) return base
    return base * calculateExponent(base,--exponent)
}

//依次比较10次幂,100次幂,1000次幂,10000次幂循环100次耗时
console.time()
for(let i =0;i<100;i++){
    calculateExponent(i,10)
}
console.timeEnd()

console.time()
for(let i =0;i<100;i++){
    Math.pow(i,10)
}
console.timeEnd()

console.time()
for(let i =0;i<100;i++){
   i ** 10
}
console.timeEnd()

touchStart(index, fatherIndex) {
  this.clientX = null
  this.clientY = null
},
touchMoving(index, fatherIndex, event) {
  this.clientX = event.detail.x + (this.moveAreaWidth / 4 / 2) //this.moveAreaWidth每个modal
  this.clientY = event.detail.y + ITEM_HEIGHT / 4
},
touchEnd(index, fatherIndex) {
  if (this.clientX && this.clientY) {
    const row = Math.floor(this.clientY / (ITEM_HEIGHT / 2))
    const column = Math.floor(this.clientX / (this.moveAreaWidth / 4))
    const newIndex = row * 4 + column
    index == newIndex ? this.hasChangedSort = false : (this.hasChangedSort = true,this.handleDragEnd(index, fatherIndex, newIndex))
  }
}

props = {
        text: {
          type: String,
          default: '正在加载'
        }
      }

props = {
        someprop: {
          type: String,
          default: 'someText',
          required: true
        }
      }

import React from 'react'
import PropTypes from 'prop-types'
class MyComponent extends React.Component {
  render() {
    // ... do things with the props
  }
}
MyComponent.propTypes = {
    someProps:PropTypes.string.isRequired
}

Component({
  lifetimes: {
    attached() {
      // 在组件实例进入页面节点树时执行
    },
    detached() {
      // 在组件实例被从页面节点树移除时执行
    },
  },
  // 以下是旧式的定义方式，可以保持对 <2.2.3 版本基础库的兼容
  attached() {
    // 在组件实例进入页面节点树时执行
  },
  detached() {
    // 在组件实例被从页面节点树移除时执行
  },
  // ...
})

//子组件
class ChildComponent extends React.Components {
  render() {
    return (
      <button onClick={
        () => {
          this.props.clickHandler('This is a click')
        }
      }></button>
    )
  }
}
//父组件
import ChildComponent from './child-component'

class ParentComponent extends React.Components {
  clickHandler(message) {
    console.log(message)
  }

  render() {
    return (
      <child-component
        clickHandler={ this.clickHandler.bind(this) }
        />
    )
  }
}

   import {Observable} from 'rxjs/Rx'

   const $video = document.querySelector('#video')
const $anchor = document.querySelector('#anchor')
const scroll = Observable.fromEvent(document, 'scroll').    //监听document事件
	map(e => $anchor.getBoundingClientRect().bottom < 0).  //map将event事件映射为判断式布尔值
	subscribe(bool => {                                   //如果当前元素不在视窗内,则改变样式
		if(bool){
			$video.classList.add('video-fixed')
		}else{
			$video.classList.remove('video-fixed')
			$video.style.transform = ''
		}
	})

const mouseDown = Observable.fromEvent($video, 'mousedown') //observe事件
const mouseMove = Observable.fromEvent(document, 'mousemove')
const mouseUp = Observable.fromEvent(document, 'mouseup')

const videoBoundingRect = $video.getBoundingClientRect() //获取viedo元素rect对象
const validValue = (value,max,min)=>{                    //比较函数,防止拖拽出屏幕
	return Math.min(Math.max(value,min),max)
}
mouseDown.filter(e => $video.classList.contains('video-fixed')). //filter过滤
	switchMap(e => mouseMove.takeUntil(mouseUp)). //将高阶Oberve转换为低阶
	withLatestFrom(mouseDown, (move, down) => {  //结合上一个observable源的结果
		return {  //move.clientX - down.offsetX =>处理抖动
			x: validValue(move.clientX - down.offsetX,window.innerWidth - videoBoundingRect.width/2,0),
			y: validValue(move.clientY - down.offsetY,window.innerHeight - videoBoundingRect.height/2,0),
		}
	}).
	subscribe(e => {
		$video.style.transform = `translate3D(${e.x}PX,${e.y}px,0)`
	})