如何封装$on,$emit,$off——学vue前你必须懂得封装！

let evevtListenr = {}

封装$on

const $on = (eventName,cb)=>{

    if(!evevtListenr[eventName]){

        evevtListenr[eventName] =[];

    }

    evevtListenr[eventName].push(cb);

    }

    封装$emit

const $emit = (eventName,params)=>{

        if(evevtListenr[eventName]){

            evevtListenr[eventName].map((cb)=>{

                cb(params);

            })

        }

    }

封装$off

    const $off = (eventName,cb)=>{

        if(evevtListenr[eventName]){

            if(cb){

            let index=vevtListenr[eventName].indexof(cb);

            evevtListenr[eventName].splice(index,1);

            }else{

                evevtListenr[eventName].length=0;

            }

        }

    }

    

    function fn1(val){

        console.log(111,val);

    };

    function fn2(val){

        console.log(222,val);

    };

    function fn3(val){

        console.log(333,val);

    }

    $on('work1',fn1);

    $on('work1',fn2);

    $on('work1',fn3);

    $emit('work1');