In HTML, JavaScript statements are "instructions" to be "executed" by the web browser.

This statement tells the browser to write "Hello Dolly." inside an HTML element with id="demo":

Example:

document.getElementById("demo").innerHTML = "Hello Dolly.";

 

Most JavaScript programs contain many JavaScript statements.

The statements are executed, one by one, in the same order as they are written.

In this example x, y, and z are given values, and finally z is displayed:

Example:

var x, y, z;
x = 5;
y = 6;
z = x + y;
document.getElementById("demo").innerHTML = z;

 

JavaScript programs (and JavaScript statements) are often called JavaScript code.

Semicolons separate JavaScript statements.

Add a semicolon at the end of each executable statement:

Example:

var a, b, c;
a = 5;
b = 6;
c = a + b;

 

When separated by semicolons, multiple statements on one line are allowed:

a = 5; b = 6; c = a + b;

 

On the web, you might see examples without semicolons.

Ending statements with semicolon is not required, but highly recommended.

JavaScript ignores multiple spaces. You can add white space to your script to make it more readable.

The following lines are equivalent:

Example:

var person = "Hege";
var person="Hege";

 

A good practice is to put spaces around operators ( = + - * / ):

var x = y + z;

 

For best readability, programmers often like to avoid code lines longer than 80 characters.

If a JavaScript statement does not fit on one line, the best place to break it, is after an operator:

Example:

document.getElementById("demo").innerHTML =
"Hello Dolly!";

 

JavaScript statements can be grouped together in code blocks, inside curly brackets {...}.

The purpose of code blocks is to define statements to be executed together.

One place you will find statements grouped together in blocks, is in JavaScript functions:

Example:

function myFunction() {
    document.getElementById("demo1").innerHTML = "Hello Dolly!";
    document.getElementById("demo2").innerHTML = "How are you?";
}

 

In this tutorial we use 4 spaces of indentation for code blocks.

You will learn more about functions later in this tutorial.

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

Example:

(5 + 6) * 10

 

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

Example:

var x, y;
x = 5;
y = 6;/code>