事件总线

class LQEventBus {
    constructor() {
        this.eventBus = {}
    };
    on(eventName,callBack,thisArg) {
        let handers = this.eventBus[eventName]
        if(!handers) {
            handers = []
            this.eventBus[eventName] = handers
        }
        handers.push({
            callBack,
            thisArg
        })
    };
    emit(eventName,payLoad) {
        let handers = this.eventBus[eventName]
        handers.forEach(hander => {
            hander.callBack.apply(hander.thisArg,payLoad)
        });
    };
    off(eventName,callBack) {
        let handers = this.eventBus[eventName]
        if(!handers) return
        const newHanders = [...handers]
        for(let i = 0;i <newHanders.length;i++) {
            if(callBack == newHanders[i].callBack) {
                const index = handers.indexOf(newHanders[i])
                if(index !== -1) {
                    handers.splice(index,1)
                }
            }
        }

    }
}


// 测试代码
const eventBus = new LQEventBus()

function bar() {
    console.log('bar')
}
eventBus.on('abc',function() {
    console.log("abc1")
})

eventBus.on('abc2',function() {
    console.log("abc2")
})


eventBus.on('abc',bar)
eventBus.off('abc',bar)


eventBus.emit('abc')
eventBus.emit('abc2')