js notes 6 object literals create objects

Create objects using object literals

//用对象字面量声明对象font，包含属性size，值为16；方法changeFontsize，形参为n，方法(函数)体如下，方法(函数)中访问size
const font ={
  size:16,
 changeFontsize(n){
    if (this.size+n < 14 || this.size+n > 22){
      return;
    }
    size+= n;
    document.body.style.fontSize = size + 'px';}}

Access the object's key:

(1) Object.Key name

Assigning a value to a key that does not exist in the object will add the key/value pair

let obj={'a':5,b:1,doit:function(){}};
obj.a=6;
obj.c=8;
let x=obj.a;
let y=obj.doit();
obj.d;   obj.f();//调用不存在的方法会出错

(2) object [key name]

Key names can be primitive data types or expressions (variables)

[ ] can be accessed. Keys that cannot be accessed will not go wrong with [ ]

let obj={width:60,'font-size':9};
obj['width']=80;
obj['font-size']=16;
let key='id';
obj[key]='top';

Iterate over the keys and values ​​of an object

for(variable in object)

let person={name:'小明'，
age:'20'}
for (let key in person){
console.log(key+":"+person[key]);}

for (variable of iterable objects)

same as above