一、发布订阅模式

class Dep {
    constructor() {
        this.clientList = {};
    }
    listen(key, fn) {
        if (!this.clientList[key]) {
            this.clientList[key] = [];
        }
        this.clientList[key].push(fn);
    }
    trigger(key, ...arg) {
        const stack = this.clientList[key];
        if (!stack || stack.length === 0) return;
        for (const fn of stack) {
            if (typeof fn !== 'function') continue;
            fn.applay(this, arg);
        }
    }
    remove(key, fn) {
        const stack = this.clientList[key];
        if (!stack || stack.length === 0) return;
        for (let i = 0, len = stack.length; i < len; i++) {
            const _fn = stack[i];
            if (_fn === fn) {
                stack.splice(i, 1);
                break;
            }
        }
    }
}

export const installEvent = obj => {
    Object.assign(obj, new Dep());
}

export default new Dep();