Using String Methods


The JavaScript String object provides many handy-dandy methods. Table 9-1 shows the most important of these string methods.

Besides the string methods shown in Table 9-1, the String object has one property, length. The length property contains the number of characters in a string.

Table 9-1: Selected String Object Manipulation Methods

Method

Description

charAt()

Returns the character at a given position in a string

concat()

Concatenates one or more values to a string

indexOf()

Searches a string for a substring or character; returns the first occurrence of the substring or character

lastIndexOf()

Searches a string backwards for a substring or character; returns the first occurrence

split()

Splits a string into an array of strings using a specified delimiter character to make the break

substring()

Extracts a portion of a string

toLowerCase()

Converts a copy of a string to all lower case

toUpperCase()

Converts a copy of a string to all upper case

In order to use one of these String object methods, as usual you need to create a string instance based on the object. You can do this in a number of ways. We’ve already used many of them throughout this book.

Methods for creating String objects include the following:

  • Using the String constructor, for example, var x = new String ("Hello");

  • Using the String() conversion function

  • Using an object’s toString method

  • Simply assigning a literal text string to a variable

Once you’ve created a string instance, you can use it to invoke a string method in the usual fashion (see Chapter 7, “ Working with Objects,” if you need a refresher course on how objects work in JavaScript).

To Use a String Object Method:

  1. Create a variable containing a string. For example:

     var myStr = "Beasts of England"; 

  2. Use the dot operator to apply a string method to the string. For example:

     var newStr = myStr.toLowerCase(); 

In the example, newStr would contain the string beasts of england.

String Methods Used to Generate HTML

You should also know that besides the methods shown in Table 9-1 there are a whole slew of methods that are used to make a copy of a string embedded in HTML tags. This makes sense because as a language JavaScript is widely used to output HTML. Table 9-2 describes these methods.

Table 9-2: Selected HTML Generation Methods of the String Object

Method

Description

anchor()

Places a copy of the string within an HTML anchor

blink()

Places a copy of a string within <BLINK> </BLINK> tags

bold()

Places a copy of the string with <BOLD> </BOLD> tags

fontcolor()

Uses the color attribute of the <FONT> tag to change the color in which the string is displayed

fontsize()

Uses the size attribute of the <FONT> tag to change the font in which the string is displayed

link()

Creates a hypertext link around a copy of the string

Because these methods are pretty simple to figure out if you need to, and they’re not widely useful beyond using JavaScript to build pages for the Web, I won’t go into them in detail. However, I will show you a quick example so you can get the gist.

Using the Link Method

The following shows how you’d create an HTML hyperlink using the String object’s link method.

To Create and Display a Link:

  1. Create a string. For example:

     linkText = "Apress"; 

  2. Use the link method of the String object to add a hyperlink to the string:

     linkText.link("http://www.apress.com") 

  3. Display the results using the document.write method:

     document.write(linkText.link("http://www.apress.com")); 

  4. Open an HTML page containing the code, as shown in Listing 9-1, in a browser. The link will appear like any hyperlink, with the URL it points to appearing in the browser’s status bar (see Figure 9-1).

    Listing 9.1: Using the String Object’s Link Method

    start example
     <HTML> <HEAD> <TITLE>  A link is a link is a link...  </TITLE> </HEAD> <BODY> <H1> <SCRIPT>     linkText = "Apress";     document.write(linkText.link("http://www.apress.com"));  </SCRIPT> </H1> </BODY> </HTML> 
    end example

    click to expand
    Figure 9-1: The String object’s link method is a quick way to create a hyperlink.

It’s time to move on and start having some fun playing with strings!




Learn How to Program Using Any Web Browser
Learn How to Program Using Any Web Browser
ISBN: 1590591135
EAN: 2147483647
Year: 2006
Pages: 115
Authors: Harold Davis

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