Javascript Object对象类型使用详解

const obj =  { name: 'ian',age: 21};
//key使用变量
const gender = 'gender';
const obj =  { [gender]: 'male'};

const user = {name:'ian', age:21, 5:5};
user.name;
//使用方括号运算符
var name = 'name';
user[5];  //5
user[name]; //'ian'

const user = {};
user.name = 'ian';
const age = 'age';
user[age] = 21;

const user = {name:'ian', age:21};
delete user.name; //true
console.log(user); //{age:21}

var user = {};
delete user.name; //true
var obj = Object.defineProperty({},'name',{
  value: 'ian',
  configurable: false,
});
delete obj.name; //false
console.log(obj); //{name: 'ian'}

function User(){};
User.prototype.name = 'ian';
const user = new User();
delete user.name; //true
console.log(user.namr); //ian

const user = {name:'ian', age:21};
Object.keys(user).forEach(key=>{
  console.log(user[key]);
})

const user = { name: 'ian', age: 21 };
for (let key in user) {
  console.log(`key: ${key}, value:${user[key]}`)
}

    function User(name, age) {
      this.name = name;
      this.age = age;
    };
    User.prototype.gender = 'male';
    var user = new User('ian', 21);
    Object.defineProperty(user, 'email', {
      enumerable: false,
      value: '12345@163.com'
    });
    console.log(user);  //{name:'ian', age:'21', email:'12345@163.com'}
    console.log(Object.keys(user));  //Array [ "name", "age" ]
    for (let key in user) {
      console.log(`key: ${key}, value:${user[key]}`);
    };
    //  key: name, value:ian
    //  key: age, value:21
    //  key: gender, value:male

    for (let key in user) {
      if(user.hasOwnProperty(key)){
        console.log(`key: ${key}, value:${user[key]}`);
      }
    };
    //  key: name, value:ian
    //  key: age, value:21

const user = {name:'ian', age:21};
'name' in user; //true

user.hasOwnProperty(age); //true

const user = {name:'ian', age:21};
with(user){
 name = 'jack';
 age = 23;
}
//等同于 user.name='jack'; user.gender='male'

width(obj){
  obj.x
}
//无法判断x是obj的属性还是全局变量
with({}){
  name = 'ian';
}
//会在全局声明name变量