函数返回时不应该返回NaN

Question

为什么myTodos.meetDone（）函数返回Nan？ 它当然是js我只是定义一个名为myTodos的对象，而我只想打印console.log（）结果。

let myTodos = {
    day: 'Monday',
    meetings: 0,
    meetDone: 0,


    addMeeting: function (num) {
        this.meetings = this.meetings + num;
    },
    meetDone: function (num) {
        this.meetDone = this.meetDone - num;
    },
    resetDay: function () {
        this.meetings = 0;
        this.meetDone = 0;
    },
    report: function () {
        let meetleft = this.meetings + this.meetDone;
        return `Yo have ${meetleft} meeting for today!`;
    },
}

myTodos.addMeeting(2);
myTodos.addMeeting(5);
myTodos.meetDone(23);

console.log(myTodos);

console.log(myTodos.report());

首先，console.log用于调试 为什么它回归南我不理解这个!!!!

Answer 1

正如@AndrewBone在评论中已经提到的，您的对象有两个名为meetDone的属性。后者覆盖了第一个，因此当您添加this.meetings + this.meetDone时，您将向一个数字添加一个函数，导致显示NaN。更改其中一个属性的名称，meetingDone比meetDone IMO更具描述性

let myTodos = {
    day: 'Monday',
    meetings: 0,
    meetDone: 0,


    addMeeting: function (num) {
        this.meetings = this.meetings + num;
    },
    meetingDone: function (num) {
        this.meetDone = this.meetDone - num;
    },
    resetDay: function () {
        this.meetings = 0;
        this.meetDone = 0;
    },
    report: function () {
        let meetleft = this.meetings + this.meetDone;
        return `Yo have ${meetleft} meeting for today!`;
    },
}

myTodos.addMeeting(2);
myTodos.addMeeting(5);
myTodos.meetingDone(23);

console.log(myTodos);

console.log(myTodos.report());