6、 JS naming rules and specifications

1、 identifier

An identifier is a word , A name
Constant names 、 Variable name 、 Function names are identifiers
keyword 、 Reserved words are also identifiers

2、 Naming rules

1、 By letter 、 Numbers 、 Underline and $ The symbols make up , Cannot start with a number
2、 Can't be keywords and reserved words
3、 Case sensitive

3、 Naming specification

1、 Variable names are best known by name
2、 Little hump nomenclature ： Initial lowercase , The first letter of the following words needs to be capitalized **（ recommend ）**

var userName = "wc"; //  Little hump nomenclature 
var UserName = "xq"; //  The name of the great hump 
var user_name = "xx"; //  Underline nomenclature