Identifiers:

1)JavaScript identifiers are names, which are given to variables, functions etc.
2)The names must start with a letter or underscore or $ symbol.
3)JS variable is case sensitive.
4)Name and name are two different variables.
5)Syntax: var variable_name=value.
6)Ex: var a=10;

Literal

A literal is a possible values,which are given to variable.

1)Integer literals

Ex: 123(decimal value), 7b(hexadecimal value), 172(octal value).

2)Floating number literals

EX: 8.34, -4.2

3)Boolean literals

Ex: true,false

4)String literals

EX: "uma","100"

5)Object literals

EX: var userName= {

       name : "uma"

       };

6)Array literals

Ex: var names = ["uma","maheswari"];

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Variables:

• Var is the keyword in JS to define variables.
• Variable can hold any type of value.
• Syntax: var var_name=value.

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Expressions:

• An expression is a valid set of literals,variables,operators.
• Expression is used to evaluate a single value.
• Syntax:value=operand operator operand (or) operand=value.
• Ex:a=3+4, a=7.

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Comments:

• Comments are used to explain the source code.
• // is used for single line comments.
• /* and */ are used for double line comments.
• Code which is in comments that won't execute.

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JavaScript & Camel Case:

• JS is Case-sensitive.
• In JS, identifiers(variables & functions) should be in Camel Case
• We can use underscores but not '-'.
• We can use upper camel case. Ex: FirstName.
• We can use lower camel case. Ex: firstName.