1.在看vue源碼相關(guān)的帖子中看到這個(gè)函數(shù)：

class Dep () {
    constructor () {
        this.subs = [];
    }

    addSub (sub: Watcher) {
        this.subs.push(sub)
    }

    removeSub (sub: Watcher) {
        remove(this.subs, sub)
    }
    
    notify () {
        // stabilize the subscriber list first
        const subs = this.subs.slice()
        for (let i = 0, l = subs.length; i < l; i++) {
            subs[i].update()
        }
    }
}

這里的Watcher也是一個(gè)class對(duì)象，那么這里的(sub: Watcher)是一個(gè)鍵值對(duì)？那不是應(yīng)該要有中括號(hào)嗎？還是我理解岔了？