JavaScript Development Tools:
One of JavaScript's strengths is that expensive development tools are
not usually required. You can start with a simple text editor such as Notepad.
Since it is an interpreted language inside the context of a web
browser, you don't even need to buy a compiler.
To make our life simpler, various vendors have come up with very nice
JavaScript editing tools. Few of them are listed here:
· Microsoft FrontPage: Microsoft has developed a popular HTML
editor called FrontPage. FrontPage also provides web developers with a number
of JavaScript tools to assist in the creation of an interactive web site.
·
Macromedia Dreamweaver MX: Macromedia Dreamweaver MX
is a very popular HTML and JavaScript editor in the professional web
development crowd. It provides several handy prebuilt JavaScript components,
integrates well with databases, and conforms to new standards such as XHTML and
XML.
·
Macromedia HomeSite 5: This provided a well-liked
HTML and JavaScript editor, which will manage their personal web site just
fine.
Java Script
A JavaScript consists of JavaScript statements that are placed within
the <script>... </script> HTML tags in a web page.
You can place the <script> tag containing your JavaScript
anywhere within you web page but it is preferred way to keep it within the
<head> tags.
The <script> tag alert the browser program to begin interpreting
all the text between these tags as a script. So simple syntax of your
JavaScript will be as follows
<script ...>
JavaScript code
</script>
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The script tag takes two
important attributes:
·
language: This attribute specifies what scripting language
you are using. Typically, its value will be javascript
·
type: This attribute is what is now recommended to
indicate the scripting language in use and its value should be set to "text/javascript".
So your JavaScript segment
will look like:
<script language="javascript" type="text/javascript">
JavaScript code
</script>
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Your First JavaScript Script:
Let us write our class example to print out "Hello World".
<html>
<body>
<script language="javascript" type="text/javascript">
<!--
document.write("Hello World!")
//-->
</script>
</body>
</html>
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We added an optional HTML comment that surrounds our Javascript code.
This is to save our code from a browser that does not support Javascript. The
comment ends with a "//-->". Here "//" signifies a
comment in Javascript, so we add that to prevent a browser from reading the end
of the HTML comment in as a piece of Javascript code.
Next, we call a function document.write which writes a string
into our HTML document. This function can be used to write text, HTML, or both.
So above code will display following result:
Hello World!
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.
Whitespace and Line Breaks:
JavaScript ignores spaces, tabs, and newlines that appear in JavaScript
programs.
Because you can use spaces, tabs, and newlines freely in your program
so you are free to format and indent your programs in a neat and consistent way
that makes the code easy to read and understand.
Semicolons are Optional:
Simple statements in JavaScript are generally followed by a semicolon
character, just as they are in C, C++, and Java. JavaScript, however, allows
you to omit this semicolon if your statements are each placed on a separate
line. For example, the following code could be written without semicolons
<script language="javascript" type="text/javascript">
<!--
var1 = 10
var2 = 20
//-->
</script>
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But when formatted in a single line as follows, the semicolons are required:
<script language="javascript" type="text/javascript">
<!--
var1 = 10; var2 = 20;
//-->
</script>
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NOTE: It is a good programming practice to use semicolons
.
Case Sensitivity:
JavaScript is a case-sensitive language. This means that language
keywords, variables, function names, and any other identifiers must always be
typed with a consistent capitalization of letters.
So identifiers Time, TIme and TIME will have
different meanings in JavaScript.
NOTE: Care should be taken while writing your variable and function names in
JavaScript.
Comments in JavaScript:
JavaScript supports both C-style and C++-style comments, Thus:
·
Any text between a // and the end of a line is treated as a comment and
is ignored by JavaScript.
·
Any text between the characters /* and */ is treated as a comment. This
may span multiple lines.
·
JavaScript also recognizes the HTML comment opening sequence <!--.
JavaScript treats this as a single-line comment, just as it does the //
comment.
·
The HTML comment closing sequence --> is not recognized by
JavaScript so it should be written as //-->.
Example:
<script language="javascript" type="text/javascript">
<!--
// This is a comment. It is similar to comments in C++
/*
* This is a multiline comment in JavaScript
* It is very similar to comments in C Programming
*/
//-->
</script>
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