/**
 * 事件委托函数封装
 * @param {*} el 
 * @param {*} type 
 * @param {*} fn 
 * @param {*} selector 
 */
export function addEventListener(el,type,fn,selector){
    if(typeof el === 'string'){
        el = document.querySelector(el)
    }
    if(!selector){
        el.addEventListener(type,fn)
    }else{
        //事件委托
        el.addEventListener(type,function(e){
            //获取点击事件源
            const target = e.target
            if(target.matches(selector)){
                fn.call(target,e)
            }
        })
    }
}

/**
 * 手写事件总线 -- 一个事件绑定多个回调
 */
export const eventBus = {
    //保存类型和回调的容器
    callbacks:{}
}
//注册事件
eventBus.on = function(type,callback){
    if(this.callbacks[type]){
        this.callbacks[type].push(callback)
    }else{
        this.callbacks[type] = [callback]
    }
}
//触发事件
eventBus.emit = function(type,data){
    if(this.callbacks[type] && this.callbacks[type].length > 0){
        this.callbacks[type].forEach(callback => {
            callback(data)
        });
    }
}
//注销事件
eventBus.off = function(eventName){
    if(eventName){
        delete this.callbacks[eventName]
    }else{
        this.callbacks[type] = {}
    }
}