JavaScript Syntax

JavaScript syntax is the set of rules, how JavaScript programs are constructed:

var x, y, z;       // How to declare variablesx = 5; y = 6;      // How to assign valuesz = x + y;         // How to compute values

JavaScript Values

The JavaScript syntax defines two types of values: Fixed values and variable values.

Fixed values are called literals. Variable values are called variables.

In a programming language, variables are used to store data values.

JavaScript uses the var keyword to declare variables.

An equal sign is used to assign values to variables.

JavaScript uses arithmetic operators ( + - * / ) to compute values

An expression is a combination of values, variables, and operators, which computes to a value.

The computation is called an evaluation.

JavaScript keywords are used to identify actions to be performed.

Identifiers are names.

In JavaScript, identifiers are used to name variables (and keywords, and functions, and labels).

The rules for legal names are much the same in most programming languages.

In JavaScript, the first character must be a letter, or an underscore (_), or a dollar sign ($).

Subsequent characters may be letters, digits, underscores, or dollar signs.

Numbers are not allowed as the first character.
This way JavaScript can easily distinguish identifiers from numbers.

All JavaScript identifiers are case sensitive.

The variables lastName and lastname, are two different variables.