01. Basic data type

Time:2021-3-6
Basic data types (7)
number 1,2,3……
string Hello, Hello, hello
boolean false/ true
null  
undefined  
symbol  
object arr/fuction

Identifier:All user-defined names are called identifiers

1. Cannot start with a number

2. Case sensitive (name and name are two variables)

3. The identifier is generally known by name