Programming Tutorials

Retrieving a Portion of a String

By: aathishankaran  

You can retrieve a portion of a string variable or literal by using the substring() method. It has two parameters-the start position and end position of the substring you want to return. Just like indexOf() and lastIndexOf(), this method is also zero-based, such that the first position of the string begins at 0. For example, the following code returns New: 

"New England".substring(O,3) 

If you want to retrieve a single character, you can use charAt(). The charAt() method returns the character at the position you specify as a parameter. For example, the following code re-turns a value of v:

                "Denver Broncos".charAt(3) 

If you specify a position that is out of the range of the string, a value of -1 is returned: 

"OO7".charAt(20102)

Formatting Strings 

JavaScript has several methods you can use to format strings. Most of these methods are simply equivalents of HTML formatting tags. Using the formatting methods gives you an object-oriented way of dealing with HTML formatting tags, and it's also easier than continuously concatenating HTML tags to strings. In other words, if you have a string literal "This is the day" and you want to add bold formatting to it, you could do so using one of two means. 

First, you could add HTML formatting tags: 

"<B>" + "This is the day" + "</B>"  

Second, you could use the String object method bold () to add the formatting:

"This is the day".  

When you use this string, the following HTML text is returned: 

"<B> This is the day</B>"  

If you have a string variable called dayVar that contains the "This is the day" text, you could use the same two options: 

dayVar = "This is the day" "<B>" + dayVar + "</B>"  

The preceding code accomplishes the same thing as the following: 

dayVar = "This is the day" dayVar.bold()  

Keep in mind the context in which you can use the formatting methods. You cannot use them outside a JavaScript script as a substitute for HTML formatting tags. 

String Method	Example Returns	HTML Code
anchor("anchorName")	"Section3".anchor	<A NAME="Section3">Section('Section3")3</A>
big()	"Just save the name". big()	<BIG>Just save the name</BIG>
Blink()	“Why ask why".blink()	<BLlNK>Why ask why</BLlNK>
Boid()	"Liveandlearn".bold()	<B>Liveandlearn</B>
Fixed()	"JavaScriptcode".fixed()	<TT>JavaScript code</TT>
fontcolor("color")	"JavaPrograms",fontcolor("green")	<FONTCOLOR"green">JavaPrgrams</FONT>
fontsize(size)	"Impact".fontsize(3)	<FONT SIZE="3">lmpact</FONT>
Italics()	"Java Script Unleashed".italics()	<I>JavaScript Unleashed</I>
Link("URL")	"See My Home Page". link("http://www.myhomepage.com/”)	<A HREF="http//www.myhomepage.com/> SeeMyHomePage</A>
Small()	"TinyTim".small()	<SMALL>Tiny Tim</SMALL>
Strike()	"GameCanceled"strike()	<STRIKE>GameCanceled</STRIKE>
Sub()	"Submarines".sub()	<SUB>Submarines</SUB>
sup()	"Superman".sup()	<SUP>Superman</SUP>
toLowerCase()	"SeeSPOTrUN".toLowerCase()	seespotrun
ToUpperCase()	"let's go to the BEACH".toUpperCase()	LET'S GO TO THE BEACH

Working with Special Characters 

When working with strings in any language, you will discover certain characters that are difficult to use. JavaScript enables you to work with these special case characters by using a backslash character (\) followed by the character or its code. Table 14.3 lists the JavaScript in line symbols. 

Symbol	Description
\t	Tab
\n	New line
\r	Carriage return
\f	Form feed
\\	Backslash
\b	Backspace
\"	Double quote
\'	Single quote

 

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