8 闭包高级，对象，构造函数，实例化

对象

• 对象中的this 永远指向对象本身。

• 对象字面量，对象直接量

  var teacher = {
    name: '张三',
    age: 20,
    height: 177,
    weight:120,
    sex: 'male',
    teach: function () {
        console.log('i am teaching JavaScript');
    },
    smoke: function () {
        this.weight--;
        console.log(this.weight);
    },
    eat: function () {
        this.weight++;
        console.log(this.weight);
    }
  }
  //这个teaacher 就是对象字面量。

  var attendance = {
    students: [],
    total:6,
    join: function (name) {
        var idx = this.students.indexOf(name);
        if (idx!==-1) {
            console.log(name + '已经到了');
            return
        }
        if (this.students.length === 6) {
            console.log('已到齐');
            return;
        }
        this.students.push(name);
    },
    leave: function (name) {
        var idx = this.students.indexOf(name);
        if (idx !== -1) {
            console.log(name + '早退');
            this.students.splice(idx, 1);
        }
    },
    classOver: function () {
        this.students = [];
    }
  }

  构造函数

  var obj = {};//对象字面量
  var obj = new Object();//对象构造函数。
  //以上两种方式创建的对象完全相同。

  自定义构造函数

• 首字母都是大写。大驼峰。

• 构造器中的this 如果构造器没有实例化，就是没有意义。
• 构造器中的this在构造函数被实例化之后才有用。

  function Teacher(opt) {
    this.name = opt.name;
    this.age  = opt.age;
    this.sex  = opt.sex;
    this.weight = weight;
    this.smoke = function () {
        this.weight--;
    }
    this.eat = function () {
        this.weight++;
    }  
  }
  var teacherOne = new Teacher({
    name: '张三',
    age: 20,
    sex: 'male',
    weight:'130'
  })
  var teacherTwo = new Teacher({
    name: '李四',
    age: 21,
    sex: 'female',
    weight:'100'
  })

  demo

1. 写一个构造函数，接受函数类型的参数，参数不定，完成参数相乘或相加。
2. 写一个构造函数。可以设置车的品牌，颜色，排量。再写一个消费者的函数，设置用户的名字。年龄，收入。通过选车的方式。实例化改用户喜欢的车。再设置车的属性。

   function Count() {
    var args = arguments;//实参
    this.count = function () {
        let num = 0;
        for (let i = 0; i < args.length; i++) {
            let val = args[i];
          //不是number 类型就直接跳过
            if (typeof (val) != 'number') {
                continue
            }
            num += val;
        }
        console.log(num)
    }
    console.log(arguments);
   }
   var c = new Count(1, 2, 3, 4, 6);
   c.count();

   ```javascript

function Car(opt) { this.brand = opt.brand; this.color = opt.color; this.output = opt.output; } function Person(opt) { this.name = opt.name; this.age = opt.age; this.income = opt.income; this.selectCar = function () { var car = new Car(opt.carOpt) console.log(this.name + ‘ s favoriate car is ‘ + car.brand); } } var personA = new Person({ name: ‘PA’, age: 20, income: 20000, carOpt:{ brand: ‘BMW’, color: ‘pink’, output:’2.0T’ } }) var personB = new Person({ name: ‘PA’, age: 20, income: 10000, carOpt:{ brand: ‘Benz’, color: ‘black’, output:’1.8T’ } })

```