Case Analysis of JavaScript data Type usage

This article mainly explains "JavaScript data type use example analysis". The explanation content in this article is simple and clear, easy to learn and understand. Please follow the idea of Xiaobian and go deep into it slowly to study and learn "JavaScript data type use example analysis" together.

(1) Boolean boolean

Boolean (logical) can have only two values: true or false

var x=true;

var y=false;

(2) null and undefined

null means no object, no value here

undefined means missing value, should have value but not defined

var x = null;

var y = undefined

（3）symbol

Symbol function can accept a string as a parameter, providing a description for the newly created Symbol, used to display it on the console or as a string, easy to distinguish

let name = Symbol();

let name2 = Symbol("bb");

console.log(name); // Symbol()

console.log(typeof name); // "symbol"

console.log(name,name2); //Symbol() Symbol(bb)

console.log( name === name2); // false

(4) Object

Objects are separated by braces. Inside the brackets, the properties of the object are defined in key-value pairs (name : value). Properties separated by commas

//Spaces and breaks don't matter. Declarations can span multiple lines

var obj = {

"name":"zhang san",

"age":18

}

(The key name can also be used without quotation marks)

Reading attributes in objects:

name = obj.name

//or

name = obj['name']

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