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Table of contents
JS Basic
JS HOME
JS Introduction
JS How To
JS Where To
JS Statements
JS Comments
JS Variables
JS Operators
JS Comparisons
JS If...Else
JS Switch
JS Popup Boxes
JS Functions
JS For Loop
JS While Loop
JS Break Loops
JS For...In
JS Events
JS Try...Catch
JS Throw
JS onerror
JS Special Text
JS Guidelines

JS Objects
JS Objects Intro
JS String
JS Date
JS Array
JS Boolean
JS Math
JS RegExp
JS HTML DOM

JS Advanced
JS Browser
JS Cookies
JS Validation
JS Animation
JS Image Maps
JS Timing
JS Create Object
JS Summary

Examples/Quiz
JS Examples
JS Object Examples
JS DOM Examples
JS Quiz
JS Exam

JS References
JS Objects
JS HTML DOM

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JavaScript Statements

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JavaScript is a sequence of statements to be executed by the browser.


JavaScript is Case Sensitive

Unlike HTML, JavaScript is case sensitive - therefore watch your capitalization closely when you write JavaScript statements, create or call variables, objects and functions.


JavaScript Statements

A JavaScript statement is a command to the browser. The purpose of the command is to tell the browser what to do.

This JavaScript statement tells the browser to write "Hello Dolly" to the web page:

document.write("Hello Dolly");

It is normal to add a semicolon at the end of each executable statement. Most people think this is a good programming practice, and most often you will see this in JavaScript examples on the web.

The semicolon is optional (according to the JavaScript standard), and the browser is supposed to interpret the end of the line as the end of the statement. Because of this you will often see examples without the semicolon at the end.

Note: Using semicolons makes it possible to write multiple statements on one line.


JavaScript Code

JavaScript code (or just JavaScript) is a sequence of JavaScript statements.

Each statement is executed by the browser in the sequence they are written.

This example will write a header and two paragraphs to a web page:

<script type="text/javascript">
document.write("<h1>This is a header</h1>");
document.write("<p>This is a paragraph</p>");
document.write("<p>This is another paragraph</p>");
</script>

Try it yourself.


JavaScript Blocks

JavaScript statements can be grouped together in blocks.

Blocks start with a left curly bracket {, and ends with a right curly bracket }.

The purpose of a block is to make the sequence of statements execute together.

This example will write a header and two paragraphs to a web page:

<script type="text/javascript">
{
document.write("<h1>This is a header</h1>");
document.write("<p>This is a paragraph</p>");
document.write("<p>This is another paragraph</p>");
}
</script>

Try it yourself.

The example above is not very useful. It just demonstrates the use of a block. Normally a block is used to group statements together in a function or in a condition (where a group of statements should be executed if a condition is met).

You will learn more about functions and conditions in later chapters.


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