# JavaScript Syntax

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JavaScript syntax is the rules, how JavaScript programs are constructed.

## JavaScript Programs

A computer program is a list of "instructions" to be "executed" by the computer.

In a programming language, these program instructions are called statements.

JavaScript is a programming language.

JavaScript statements are separated by semicolon.

## Example

var x = 5;
var y = 6;
var z = x + y;
Try it Yourself »

| In HTML, JavaScript programs can be executed by the web browser.

## JavaScript Statements

JavaScript statements are composed of:

Values, Operators, Expressions, Keywords, and Comments.

## 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.

## JavaScript Literals

The most important rules for writing fixed values are:

Numbers are written with or without decimals:

10.50
1001
Try it Yourself »

Strings are text, written within double or single quotes:

"John Doe"
'John Doe'
Try it Yourself »

Expressions can also represent fixed values:

5 + 6
5 * 10
Try it Yourself »

## JavaScript Variables

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

JavaScript uses the var keyword to define variables.

An equal sign is used to assign values to variables.

In this example, x is defined as a variable. Then, x is assigned (given) the value 6:

var x;
x = 6;
Try it Yourself »

## JavaScript Operators

JavaScript uses an assignment operator ( = ) to assign values to variables:

var x = 5;
var y = 6;
Try it Yourself »

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

(5 + 6) * 10
Try it Yourself »

## JavaScript Keywords

JavaScript keywords are used to identify actions to be performed.

The var keyword tells the browser to create a new variable:

var x = 5 + 6;
var y = x * 10;
Try it Yourself »

## JavaScript Comments

Not all JavaScript statements are "executed".

Code after double slashes // or between /* and */ is treated as a comment.

Comments are ignored, and will not be executed:

var x = 5; // I will be executed
// var x = 6; I will NOT be executed
Try it Yourself »

## JavaScript is Case Sensitive

All JavaScript identifiers are case sensitive.

The variables lastName and lastname, are two different variables.

lastName = "Doe";
lastname = "Peterson";
Try it Yourself »

JavaScript does not interpret VAR or Var as the keyword var.

| It is common, in JavaScript, to use camelCase names. You will often see names written like lastName (instead of lastname).

## JavaScript Character Set

JavaScript uses the Unicode character set.

Unicode covers (almost) all the characters, punctuations, and symbols in the world.

For a closer look, please study our Complete Unicode Reference.

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