-Variables are derived from mathematics and are abstract concepts in computer languages ​​that can store calculation results or represent values -Variables can be accessed through variable names -Z1h language variable names are composed of letters, numbers, symbols and other characters, the first character cannot be a number

the general form is used to declare variables keyword var: var variable name = variable value

may involve multiple variables:

variable name variable value 1 = 1, variable name 2 = variable value 2 ; 


variable name 1, variable name 2 = variable value 1, the variable value of 2; 

global variable

using: =connected variable name and value, may declare a global variable

name: = "aaa" 


of variables-Variables declared in var within functions, loops and other code blocks, scope is limited to this code block -if var variable declaration is not used, directlyvariable name = variable When the value is, if the variable name already exists, the value will be overwritten, otherwise a ** global variable ** will be created- the variable declared withvariable name: = variable value will become the global variable directly