js--variable declarations, variable types, naming conventions

Variable declaration:

JavaScript is a weakly typed language whose variable type is determined by its value, and VAR is a variable declaration.

Variable type:

Base type: Number, String, Boolean (Boolean type: var a=true/false;), undefined (undefined type: var A;), null (Null object type var)

Composite type: Object (objects Type)

Naming conventions:

1) Case-sensitive

2) The first character must be a letter, underscore, dollar sign $

3) Other characters can be letters, underscores, dollars, or numbers

js--variable declarations, variable types, naming conventions