JavaScript Statements

var x, y, z;    // Statement 1x = 5;          // Statement 2y = 6;          // Statement 3z = x + y;      // Statement 4

JavaScript Programs

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

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

A JavaScript program is a list of programming statements.

In HTML, JavaScript programs are executed by the web browser.

JavaScript Statements

JavaScript statements are composed of:

Values, Operators, Expressions, Keywords, and Comments.

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

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

Semicolons ;

Semicolons separate JavaScript statements.

Add a semicolon at the end of each executable statement:

var a, b, c;     // Declare 3 variablesa = 5;           // Assign the value 5 to ab = 6;           // Assign the value 6 to bc = a + b;       // Assign the sum of a and b to c

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

a = 5; b = 6; c = a + b;

JavaScript White Space

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

The following lines are equivalent:

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

JavaScript Line Length and Line Breaks

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:

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

JavaScript Code Blocks

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:

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