JS Statements Java Script | Course

A computer program is a list for a computer to "run" the instructions. These instructions are referred to as statements in a programming language.

Example:

<!DOCTYPE html>
<html>
<body>

<h2>JavaScript Statements</h2>
<p>A <b>Java Script program</b> is a list of <b>statements</b> to be executed by a computer.</p>
<p id="demo"></p>
<script>var x, y, z; // Statement 1
x = 3; // Statement 2
y = 5; // Statement 3
z = x + y; // Statement 4

document.getElementById("demo").innerHTML =
"The value of z is " + z + "."; 
</script>

</body>
</html>

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

Output:

JavaScript Statements

A Java Script program is a list of computer statements.

The value of z is 8.

The declarations in Java Script include: values, operators, expressions, keywords and commentary. This statement says to the browser "Hello UK" to write "id="demo" inside a HTML element:

Example:

<!DOCTYPE html>
<html>
<body>

<h2>Java Script Statements</h2>
<p>In HTML, Java Script statements are executed by the browser.</p>
<p id="demo"></p>
<script>
document.getElementById("demo").innerHTML = "Hello UK.";
</script>

</body>
</html>

Most Java Script programs contain many Java Script statements. The declarations are performed in the same order as they are written one by one.

Note: Java Script programs (and Java Script statements) are often called Java Script code.

Output:

Java Script Statements

In HTML, Java Script statements are executed by the browser.

Hello UK.

Semicolons separate Java Script statements. Add a semicolon at the end of each executable statement:

Example:

<!DOCTYPE html>
<html>
<body>

<h2>Java Script Statements</h2>
<p>Java Script statements are separated by semicolons.</p>
<p id="demo1"></p>
<script>
var a, b, c;
a = 5;
b = 6;
c = a + b;
document.getElementById("demo1").innerHTML = c;
</script>

</body>
</html>

Output:

Java Script Statements

Java Script statements are separated by semicolons.

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

Example:

<!DOCTYPE html>
<html>
<body>
<h2>JavaScript Statements</h2>
<p>Multiple statements on one line is allowed.</p>
<p id="demo1"></p>
<script>
var a, b, c;
a = 5; b = 6; c = a + b;
document.getElementById("demo1").innerHTML = c;
</script>
</body>
</html>

Note: Without semicolons, we can see examples in the web. Semicolon termination statements are not necessary but strongly recommended.

Output:

Java Script Statements

Multiple statements on one line is allowed.

Java Script ignores multiple spaces. To make your script more readable, we can add white space to it.

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 Java Script statement does not fit on one line, the best place to break it is after an operator:

Example:

<!DOCTYPE html>
<html>
<body>

<h2>Java Script Statements</h2>
<p>Java Script code blocks are written between { and }</p>
<button type="button" onclick="myFunction()">Click Me!</button>
<p id="demo1"></p><p id="demo2"></p>
<script>
function myFunction() {
document.getElementById("demo1").innerHTML = "Hello UK!";
document.getElementById("demo2").innerHTML = "We Love Uttarakhand";
}
</script>

</body>
</html>

Output:

Java Script Statements

Java Script code blocks are written between { and }

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

Java Script statements often start with a keyword to identify the Java Script action to be performed. Here is a list of some of the keywords we will learn about in this tutorial:

Keyword	Description
break	Terminates a switch or a loop
continue	Jumps out of a loop and starts at the top
debugger	Stops the execution of JavaScript, and calls (if available) the debugging function
do ... while	Executes a block of statements, and repeats the block, while a condition is true
for	Marks a block of statements to be executed, as long as a condition is true
function	Declares a function
if ... else	Marks a block of statements to be executed, depending on a condition
return	Exits a function
switch	Marks a block of statements to be executed, depending on different cases
try ...	catch Implements error handling to a block of statements
var	Declares a variable

Note: JavaScript keywords are reserved words. Unable to use reserved words as variable names.

What are JavaScript Programs & Statements ?

JavaScript Statements

Java Script Statements

Java Script Statements

Semicolons (;)

Java Script Statements

Java Script Statements

Java Script White Space ( )

Java Script Line Length and Line Breaks

Java Script Statements

Java Script Keywords

Keyword

Description

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