import {Observable} from 'rxjs/Rx' //引入rx Observable对象

const canvas = document.querySelector('canvas')
const ctx = canvas.getContext('2d') //获取canvas画笔
ctx.beginPath()
function drawEvent([first, sec]) {
  ctx.moveTo(first.x, first.y)
  ctx.lineTo(sec.x, sec.y)
  ctx.stroke()
 }
const moveEvent = Observable.fromEvent(canvas,'mousemove')
     .map(e =>{x:e.offsetX,y:e.offsetY})
     .bufferCount(2,1) //定义move流

 const downEvent = Observable.fromEvent(canvas,'mousedown').map(()=>'down') //将Observable 结果映射为'down'

 //这里我们可以将Observable想象成一个数组,将数组的map方法类似于这里的map方法

 const upEvent = Observable.fromEvent(canvas,'mouseup').map(()=>'up') //将Observable 结果映射为'up'

 const upAndDown = downEvent.merge(upEvent) //融合两个Observable

 upAndDown.switchMap(e=>e==='down'?moveEvent:Observable.empty()).subscribe(drawEvent)
 //subscribe: 注册处理程序的订阅引用
 //因为事件处理流可能是异步的,我们不必在等待事件执行成功后再继续下一步操作,而是订阅一个注册事件,事件执行后再通知给订阅者

class EventEmeitter{
    constructor(){
        this._events = new Map()
    }
    emit(type,context,...args){
        const handler = this._events.get(type)
        if(typeof handler !== 'function'){
            throw Error(`[${type}] 未绑定事件`)
        }
        if(args.length >= 3){
            handler.apply(context,args)
        }else{
            handler.call(context,...args)
        }
    }
    addEventListener(type,fn){
        if(!this._events.get(type)){
            this._events.set(type,fn)
            console.log(`[${type}] 事件绑定`)
        }else{
            throw Error(`[${type}] 事件已绑定`)
        }
    }
    removeEventListener(type){
        this._events.delete(type)
        console.log(`[${type}] 事件移除`)
    }
}

const emitter = new EventEmeitter()
emitter.addEventListener('christmas',s=>{
    console.log(`Merry ${s}`)
})
emitter.emit('christmas',this,'Christmas')
emitter.removeEventListener('Christmas')

---
[christmas] 事件绑定
Merry Christmas
[Christmas] 事件移除

var twoSum = function(nums, target) {
    for(let i=0;i<nums.length;i++){
        var result = targer - nums[i]
        var resultIndex = nums.indexOf(result)
        if(resultIndex > -1 && resultIndex !== i){
            return [i,resultIndex]
        }
    }
}
执行用时:196ms

var twoSum = function(nums, target) {
    var map = new Map()
    for(let i=0;i<nums.length;i++){
        var result = target - nums[i]
        if(map.has(result)){
            return [map.get(result),i]
        }
        map.set(nums[i],i)
    }
}
执行用时:80ms

<meta name="viewport" content="width=device-width, initial-scale=1.0, minimum-scale=1.0, maximum-scale=1.0, user-scalable=no">

initial-scale：初始缩放比例
maximum-scale：允许缩放的最大比例
minimum-scale：允许缩放的最小比例
user-scalable：是否允许手动缩放

var win=window
win.resize = {};

    var timer = null;
    var rem = 12;
    var doc = win.document;
    var docEl = doc.documentElement;

    /**
     * 刷新页面REM值
     */
    function refreshRem() {
        var width = docEl.getBoundingClientRect().width;
        width = width > 768 ? 640 : width;
        rem = width / 7.5;
        docEl.style.fontSize = rem + 'px';
    }

    /**
     * 页面缩放或重载时刷新REM
     */
    win.addEventListener('resize', function () {
        clearTimeout(timer);
        timer = setTimeout(refreshRem, 300);
    }, false);
    win.addEventListener('pageshow', function (e) {
        if (e.persisted) {
            clearTimeout(timer);
            timer = setTimeout(refreshRem, 300);
        }
    }, false);

    refreshRem();

(function () {
    function o() {
        document.documentElement.style.fontSize = (document.documentElement.clientWidth && document.documentElement.clientWidth < 768 ? document.documentElement.clientWidth : 768) / 7.5 + "px"
    }

    var e = null;
    window.addEventListener("resize", function () {
        clearTimeout(e), e = setTimeout(o, 300)
    }, !1), o()

    //3秒后检查如果html fontSize为0，手动触发计算fontSize。
    setTimeout(function () {
        if (parseInt(document.defaultView.getComputedStyle(document.documentElement).fontSize) == 0) {
            o();
        }
    }, 3000);
})(window)