17.观察者模式

var Observe = (function() {
        var _message = {}   
        return {
            regist: function(type, fn) {
                if(typeof _message[type] == 'undefined') {
                    _message[type] = [fn]
                } else {
                    _message[type].push(fn)
                }
                // console.log(_message)
            },
            fire: function(type, args) {
                if(!_message[type]) {
                    return
                }
                var events = {
                    type: type,
                    args: args || {}
                }
                // for (let index = 0; index < _message[type].length; index++) {
                //     const element = _message[type][index];
                //     element.call(this, events)
                // }
                // console.log(_message)
                i = 0,
                len = _message[type].length
                for(; i<len; i++) {
                    _message[type][i].call(this, events)
                }

            },
            remove: function(type, fn) {
                if(Array.isArray(_message[type])) {
                    for(let i = _message[type].length; i > 0; i--) {
                        const element = _message[type][i]
                        element === fn && _message[type].splice(i, 1)
                    }
                }
                // console.log(_message)

            }
        }

    })()
    Observe.regist('test', function(e) {
        console.log(e.type, e.args.msg)
    });
    Observe.fire('test', {msg: '123123213'})

    function Student(result) {
        var that = this
        that.result = result
        that.say = function() {
            console.log(that.result)
        }
    }
    Student.prototype.answer = function(question) {
        Observe.regist(question, this.say)
    }
    Student.prototype.sleep = function(question) {
        console.log('sleep')
        Observe.remove(question, this.say)
    }
    function Teacher() {}
    Teacher.prototype.ask = function(question) {
        Observe.fire(question)
    }
    let s1 = new Student('student1')
    let s2 = new Student('student2')
    let s3 = new Student('student3')
    s1.answer('question1')
    s1.answer('question2')
    s2.answer('question1')
    s3.answer('question1')
    s3.sleep('question2')
    let T1 = new Teacher
    T1.ask('question1')
    T1.ask('question2')