JS learning notes - variables

summary

The essence : Variables are programs In memory A piece of the application is used for Storing data Space .

Declare variables

var age; // Declare a name as age The variable of 

var It's a JS keyword , be used for Declare variables ( variable The meaning of a variable is ). After using this keyword to declare variables , The computer automatically allocates memory for variables .

Variable initialization

var age = 18;  // Declare the variable and assign it to 18

Declare a variable and assign a value , We call it Initialization of a variable .

Update variables

After a variable is reassigned , Its original value will Be overwritten , The value of the variable will be based on the last assigned value .

Declare multiple variables at the same time

When multiple variables are declared at the same time , Just write one var, Use... Between multiple variable names Comma separated .

var age = 10,name = 'ZS',sex = 2;

Declare variable special case

Variable naming conventions

By letter (A-Za-z)、 Numbers (0-9)、 Underline ( )、 Dollar symbol ($ ) form
Case sensitive .
Cannot start with a number .
It can't be a keyword 、 Reserved words .
Variable names must have meaning .
Follow the hump nomenclature . Initial lowercase , The first letter of the following words needs to be capitalized .eg：myFirstName