JavaScript operator data types

operator

1. Self-increment operator

let a=11;
alert(++a);

2. Assign values ​​separately

let a,b=12,13; //报错

Object destructuring assignment

let {
    
    name,age} = {
    
    name : '铁扇公主', age : 35};
console.log(name,age);

Array destructuring assignment

let [, b, c, d] = ['abc', 23, true];
console.log(b, c, d);

3. Seek multiple squares

alert(Math.pow(2,3));
alert(7/3);
alert(Math.ceil(7/3));

4. Logical operators in js

console.log(1 && 0);
console.log(1 || 0);
console.log(!0);

type of data

Number、String、Boolean、Null、Undefined、
object（包含普通对象，也包含数组和函数）

Null（空值）类型的值只有一个，就是null
    null这个值专门用来表示一个为空的对象
    使用typeof检查一个null值时，会返回object

Undefined（未定义）类型的值只有一个，就undefined
    当声明一个变量，但是并不给变量赋值时，它的值就是undefined
    使用typeof检查一个undefined时也会返回undefined

Determine the variable type

typeof(a)

coercion

There are many methods, such as converting to an integer, you can use operators such as positive and negative signs, you can parseInt, you can use the Number function.

1. Data type

let a=10;
console.log(a);
console.log(typeof(a));

a=10.1;
console.log(a);
console.log(typeof(a));

a="332432";
console.log(a);
console.log(typeof(a));

a=true;
console.log(a);
console.log(typeof(a));

a=null;
console.log(a);
console.log(typeof(a));

a=undefined;
console.log(a);
console.log(typeof(a));

a={
    
    name:'996',age:11};
console.log(a);
console.log(typeof(a));

a=[1,2,3,4];
console.log(a);
console.log(typeof(a));

a=function(){
    
    console.log('aa');}
console.log(a);
console.log(typeof(a));

2. Forced type conversion

coercion

let b="2341";
console.log(typeof(b));

implicit conversion

let b="2341";
let c=--b;
console.log(c);
console.log(typeof(c));

show transition

let b="2341";
let d=Number(b);
console.log(d);
console.log(typeof(d));

let b="2341";
let e=parseInt(b);
console.log(e);
console.log(typeof(e));