设计模式 - 发布订阅者模式

let EventListen = (function () {
    let list = {},
    trigger,
    listen,
    remove;

    // 订阅
    listen = function (key, fn) {
        if (!this.list[key]) {
            this.list[key] = []
        }
        this.list[key].push(fn)
    }

    // 发布
    trigger = function () {
        // 对应的key取出来
        let key = Array.prototype.shift.call(arguments)
        let fns = this.list[key]
        if (!fns || fns.length === 0) {
            return
        }
        for (let i = 0, fn; fn = fns[i++];) {
            fn.apply(this, arguments)
            // fn(...arguments)
        }
    }

    // 取消订阅
    remove = function (key, fn) {
        let fns = this.list[key]
        if (!fns) {
            return false
        }
        if (!fn) {
            fn && (fns.length = 0)
        } else {
            for (let i = fns.length; i >= 0; i--) {
                let _fn = fns[i]
                if (_fn === fn) {
                    fns.splice(i, 1)
                }
            }
        }
    }
    return {
        list,
        trigger,
        listen,
        remove
    }
})()

EventListen.listen('red', function (size) {
    console.log(`size是${size}`)
})
EventListen.listen('black', function (size) {
    console.log(`size是${size}`)
})
EventListen.trigger('red', 42)
EventListen.trigger('black', 43)
EventListen.trigger('black', 40)
EventListen.trigger('black', 41)