By: aathishankaran Viewed: 153215 times Printer Friendly Format
Strings area fundamental part of any programming language. Strings, which are a set of alpha-numeric characters, can be either a literal string, such as "Push the envelope" or a variable representing a string, such as the Phrase. A string can also be treated as an object, complete with its own suite of methods and properties.
Creating a String Object.
Use the following procedure to create a string object.
Var str_obj =new String([message])
var str = new String("My name is Richard" )
alert (str. length)
Working with Strings
Returns an integer representing the value of size of the string.
Returns the character at the specified index.
indexOf (searchText [,startPos])
Returns the index of the first occurrence of SearchText.
Returns the index of last occurrence of searchText
substring (startPos, endPos)
Returns the substring of the string starting at startpos and ending at endPos
Determining String Lengths
You can use the String object's length property to determine the size of a string.
For example, the following code returns 17:
"Crazy Legs Nelson".length
The following code returns 16:
var str = "This is the day." len = str.length
Searching Within Strings
You can search for text within strings by using indexOf() and lastIndexOf(). Use these methods when you want to search for a particular character or substring within a string and return the position (or index) of the occurrence within the string. Whereas indexOf() starts at the left of the string and moves right, lastIndexOfO does the same operation but starts at the left. Both indexOf() and lastIndexOfO start at the 0 position for the first character encountered, and both return a value of -1 if the search text is not found. For example, the following code re-turns a value of 3:
"Time and time again".indexOf ("e")
On the other hand, the following code returns a value of 12:
"Time and time again".lastIndexOf("e")
Both methods have an optional second parameter that enables you to specify here in the string you want to start the search. For example, the script shown n Listing 14.1 searches through the variable graf and counts the number of occurrences of the letter 'e'.
pos = 0 num = -1 i = -1
var graf = "While nearly everyone agrees on the principle of reuse,
the priority we give it varies wildly."
while (pos != -1)
pos = graf.indexOf("e",i+1)
num += 1
i = pos
document.write("There were" + num + " e' s in that paragraph.")
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