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Strings

Strings are created using the global object constructor String or created as string primitives.

String literals are string primitives and are created by enclosing some value in single or double quotes and are the preferred method of string creation unless you specifically need to use a String object.

Any string primitives have full access to String methods as JavaScript automaticially converts any string primitives to temporary String objects when a String method is called on the string primitive. Lets see an example of this.



// Create a String object.
aString = new String('happychappy'); 
// Will show the value 'y' in alert box
alert(aString.charAt(4) + ' - String object'); 

// Create a string literal and call a String() method on it.
bString = 'happychappy'; 
// Will show the value 'y' in alert box
alert(bString.charAt(4) ' + ' - string literal'); 

Press the button below to action the above code:


String Concatenation


There are a few things to remember when concatenating strings together:

  • In JavaScript we use the + symbol to join two or more strings together.
  • The JavaScript interpreter uses automatic type conversion when combining string and numbers, which means all numbers are converted to strings before concatenation takes place.

The following code should shed light on the above.



// Create a string and numeric variables.
var aString = '5';
var aNumber = 5;

// Concatenation ends up with a string holding the value  '55' not 10.
alert(aString + aNumber);

Press the button below to action the above code:


String Comparison


In JavaScript we use the < (less than) symbol and the > (greater than) symbol to compare string values as demonstrated by the following.

Don't worry about the conditional statements such as if for now as we cover this in JavaScript Intermediate Lesson 3 - Conditional Statements.



// Create a couple of strings with same value
var aString = 'String';  
var bString = 'String';

// Compare strings and alert with a message 
if (aString < bString)  
  alert(aString + ' is less than ' + bString);  
else if (aString > bString)  
  alert(aString + ' is greater than ' + bString);  
else  
  alert(aString + ' and ' + bString + ' have equal string values'); // true  

Press the button below to action the above code:


Special Character Usage in Strings

The following are escape character constants that may be required for rendering or printing and use the backslash symbol \ to signify the escape sequence.


Character Description
\bEscape a backspace
\fEscape a form feed
\nEscape a new line
\rEscape a carriage return
\tEscape a tab
\vEscape a vertical tab
\'Escape a single quote
\"Escape a double quote
\\Escape a backslash
\xXXEscape the character with the Latin-1 encoding specified by the two hexadecimal digits XX between 00 and FF
\XXXEscape the character with the Latin-1 encoding specified by up to three octal digits XXX between 0 and 377
\uXXXXEscape the Unicode character specified by the four hexadecimal digits XXXX

Reviewing The Code

There are various ways we can create and manipulate strings and we have shown some examples above. For a complete list of the methods available with the String object and their usage visit the reference section of the site.

Lesson 8 Complete

In this lesson we looked at the String object and string literals and some of the methods used for extracting data stored within them.

Related Tutorials

JavaScript Intermediate Tutorials - Lesson 9 - Regular Expressions


What's Next?

In the next lesson we look at booleans and the Boolean object.


Reference

JavaScript Reference - String constructor
JavaScript Reference - string operator
JavaScript Reference - new special operator




  

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