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10.13.2013

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Learn Javascript

Javascript Tutorial


What is JavaScript?

  • JavaScript was designed to add interactivity to HTML pages
  • JavaScript is a scripting language
  • A scripting language is a lightweight programming language
  • A JavaScript consists of lines of executable computer code
  • A JavaScript is usually embedded directly into HTML pages
  • JavaScript is an interpreted language (means that scripts execute without preliminary compilation)
  • Everyone can use JavaScript without purchasing a license

Are Java and JavaScript the Same?

NO!
Java and JavaScript are two completely different languages in both concept and design!
Java (developed by Sun Microsystems) is a powerful and much more complex programming language - in the same category as C and C++.

What can a JavaScript Do?

  • JavaScript gives HTML designers a programming tool - HTML authors are normally not programmers, but JavaScript is a scripting language with a very simple syntax! Almost anyone can put small "snippets" of code into their HTML pages
  • JavaScript can put dynamic text into an HTML page - A JavaScript statement like this: document.write("<h1>" + name + "</h1>") can write a variable text into an HTML page
  • JavaScript can react to events - A JavaScript can be set to execute when something happens, like when a page has finished loading or when a user clicks on an HTML element
  • JavaScript can read and write HTML elements - A JavaScript can read and change the content of an HTML element
  • JavaScript can be used to validate data - A JavaScript can be used to validate form data before it is submitted to a server. This saves the server from extra processing
  • JavaScript can be used to detect the visitor's browser - A JavaScript can be used to detect the visitor's browser, and - depending on the browser - load another page specifically designed for that browser
  • JavaScript can be used to create cookies - A JavaScript can be used to store and retrieve information on the visitor's computer

The Real Name is ECMAScript

JavaScript's official name is "ECMAScript". The standard is developed and maintained by the ECMA organisation. 
ECMA-262 is the official JavaScript standard. The standard is based on JavaScript (Netscape) and JScript (Microsoft).
The language was invented by Brendan Eich at Netscape (with Navigator 2.0), and has appeared in all Netscape and Microsoft browsers since 1996.
The development of ECMA-262 started in 1996, and the first edition of was adopted by the ECMA General Assembly in June 1997.
The standard was approved as an international ISO (ISO/IEC 16262) standard in 1998.
The development of the standard is still in progress.

How to Put a JavaScript Into an HTML Page

<html>
<body>
<script type="text/javascript">
document.write("Hello World!");
</script>
</body>
</html>

The code above will produce this output on an HTML page:

Hello World!

Example Explained

To insert a JavaScript into an HTML page, we use the <script> tag. Inside the <script> tag we use the "type=" attribute to define the scripting language.
So, the <script type="text/javascript"> and </script> tells where the JavaScript starts and ends:

<html>
<body>
<script type="text/javascript">
...
</script>
</body>
</html>

The word document.write is a standard JavaScript command for writing output to a page.
By entering the document.write command between the <script> and </script> tags, the browser will recognize it as a JavaScript command and execute the code line. In this case the browser will write Hello World! to the page:
<html>
<body>
<script type="text/javascript">
document.write("Hello World!");
</script>
</body>
</html>


Note: If we had not entered the <script> tag, the browser would have treated the document.write("Hello World!") command as pure text, and just write the entire line on the page.

HTML Comments to Handle Simple Browsers

Browsers that do not support JavaScript will display JavaScript as page content.
To prevent them from doing this, and as a part of the JavaScript standard, the HTML comment tag can be used to "hide" the JavaScript. Just add an HTML comment tag <!-- before the first JavaScript statement, and a --> (end of comment) after the last JavaScript statement.

<html>
<body>
<script type="text/javascript">
<!--
document.write("Hello World!");
//-->
</script>
</body>
</html>

The two forward slashes at the end of comment line (//) is the JavaScript comment symbol. This prevents JavaScript from executing the --> tag.

Where to Put the JavaScript

JavaScripts in a page will be executed immediately while the page loads into the browser. This is not always what we want. Sometimes we want to execute a script when a page loads, other times when a user triggers an event.

Scripts in the head section: Scripts to be executed when they are called, or when an event is triggered, go in the head section. When you place a script in the head section, you will ensure that the script is loaded before anyone uses it.

<html>
<head>
<script type="text/javascript">
....
</script>
</head>

Scripts in the body section: Scripts to be executed when the page loads go in the body section. When you place a script in the body section it generates the content of the page.

<html>
<head>
</head>
<body>
<script type="text/javascript">
....
</script>
</body>

Scripts in both the body and the head section: You can place an unlimited number of scripts in your document, so you can have scripts in both the body and the head section.

<html>
<head>
<script type="text/javascript">
....
</script>
</head>
<body>
<script type="text/javascript">
....
</script>
</body>

Using an External JavaScript

Sometimes you might want to run the same JavaScript on several pages, without having to write the same script on every page.
To simplify this, you can write a JavaScript in an external file. Save the external JavaScript file with a .js file extension.

Note: The external script cannot contain the <script> tag!
To use the external script, point to the .js file in the "src" attribute of the <script> tag:
<html>
<head>
<script src="xxx.js"></script>
</head>
<body>
</body>
</html>
Note: Remember to place the script exactly where you normally would write the script!

JavaScript Variables

As with algebra, JavaScript variables are used to hold values or expressions.
A variable can have a short name, like x, or a more describing name like length.  
A JavaScript variable can also hold a text value like in carname="Volvo".
Rules for JavaScript variable names:
  • Variable names are case sensitive (y and Y are two different variables)
  • Variable names must begin with a letter or the underscore character
NOTE:  Because JavaScript is case-sensitive, variable names are case-sensitive.

Example

A variable's value can change during the execution of a script. You can refer to a variable by its name to display or change its value.

Declaring (Creating) JavaScript Variables

Creating variables in JavaScript is most often referred to as "declaring" variables.
You can declare JavaScript variables with the var statement:

var x;
var carname;

After the declaration shown above, the variables has no values, but you can assign values to the variables while you declare them:

var x=5;
var carname="Volvo";
Note: When you assign a text value to a variable, you use quotes around the value.

Assigning Values to JavaScript Variables

You assign values to JavaScript variables with assignment statements:

x=5;
carname="Volvo";

The variable name is on the left side of the = sign, and the value you want to assign to the variable is on the right.
After the execution of the statements above, the variable x will hold the value 5, and carname will hold the value Volvo.

Assigning Values to Undeclared JavaScript Variables

If you assign values to variables that has not yet been declared, the variables will automatically be declared.
These statements:

x=5;
carname="Volvo";

have the same effect as:

var x=5;
var carname="Volvo";

Redeclaring JavaScript Variables

If you redeclare a JavaScript variable, it will not lose its original value.

var x=5;
var x;

After the execution of the statements above, the variable x will still have the value of 5. The value of x is not reset (or cleared) when you redeclare it.

JavaScript Arithmetic

As with algebra, you can do arithmetic with JavaScript variables:

y=x-5;
z=y+5;

You will learn more about the operators that can be used between JavaScript variables in the next chapter of this tutorial.

Conditional Statements

Very often when you write code, you want to perform different actions for different decisions. You can use conditional statements in your code to do this.
In JavaScript we have the following conditional statements:
  • if statement - use this statement if you want to execute some code only if a specified condition is true
  • if...else statement - use this statement if you want to execute some code if the condition is true and another code if the condition is false
  • if...else if....else statement - use this statement if you want to select one of many blocks of code to be executed
  • switch statement - use this statement if you want to select one of many blocks of code to be executed

If Statement

You should use the if statement if you want to execute some code only if a specified condition is true.

Syntax

if (condition)
{
code to be executed if condition is true
}
Note that if is written in lowercase letters. Using uppercase letters (IF) will generate a JavaScript error!

Example 1

<script type="text/javascript">
//Write a "Good morning" greeting if
//the time is less than 10
var d=new Date();
var time=d.getHours();
 
if (time<10) 
{
document.write("<b>Good morning</b>");
}
</script>

Example 2

<script type="text/javascript">
//Write "Lunch-time!" if the time is 11
var d=new Date();
var time=d.getHours();
 
if (time==11) 
{
document.write("<b>Lunch-time!</b>");
}
</script>

Note: When comparing variables you must always use two equals signs next to each other (==)!
Notice that there is no ..else.. in this syntax. You just tell the code to execute some code only if the specified condition is true.

If...else Statement

If you want to execute some code if a condition is true and another code if the condition is not true, use the if....else statement.

Syntax

if (condition)
{
code to be executed if condition is true
}
else
{
code to be executed if condition is not true
}

Example

<script type="text/javascript">
//If the time is less than 10,
//you will get a "Good morning" greeting.
//Otherwise you will get a "Good day" greeting.
var d = new Date();
var time = d.getHours();
 
if (time < 10) 
{
document.write("Good morning!");
}
else
{
document.write("Good day!");
}
</script>

If...else if...else Statement

You should use the if....else if...else statement if you want to select one of many sets of lines to execute.

Syntax

if (condition1)
{
code to be executed if condition1 is true
}
else if (condition2)
{
code to be executed if condition2 is true
}
else
{
code to be executed if condition1 and
condition2 are not true
}

Example

<script type="text/javascript">
var d = new Date()
var time = d.getHours()
if (time<10)
{
document.write("<b>Good morning</b>");
}
else if (time>10 && time<16)
{
document.write("<b>Good day</b>");
}
else
{
document.write("<b>Hello World!</b>");
}
</script>

The JavaScript Switch Statement

You should use the switch statement if you want to select one of many blocks of code to be executed.

Syntax

switch(n)
{
case 1:
  execute code block 1
  break;    
case 2:
  execute code block 2
  break;
default:
  code to be executed if n is
  different from case 1 and 2
}

This is how it works: First we have a single expression n (most often a variable), that is evaluated once. The value of the expression is then compared with the values for each case in the structure. If there is a match, the block of code associated with that case is executed. Use break to prevent the code from running into the next case automatically.

Example

<script type="text/javascript">
//You will receive a different greeting based
//on what day it is. Note that Sunday=0,
//Monday=1, Tuesday=2, etc.
var d=new Date();
theDay=d.getDay();
switch (theDay)
{
case 5:
  document.write("Finally Friday");
  break;
case 6:
  document.write("Super Saturday");
  break;
case 0:
  document.write("Sleepy Sunday");
  break;
default:
  document.write("I'm looking forward to this weekend!");
}
</script>

Alert Box

An alert box is often used if you want to make sure information comes through to the user.
When an alert box pops up, the user will have to click "OK" to proceed.

Syntax:
alert("sometext");

Confirm Box

A confirm box is often used if you want the user to verify or accept something.
When a confirm box pops up, the user will have to click either "OK" or "Cancel" to proceed.
If the user clicks "OK", the box returns true. If the user clicks "Cancel", the box returns false.

Syntax:
confirm("sometext");

Prompt Box

A prompt box is often used if you want the user to input a value before entering a page.
When a prompt box pops up, the user will have to click either "OK" or "Cancel" to proceed after entering an input value.
If the user clicks "OK" the box returns the input value. If the user clicks "Cancel" the box returns null.

Syntax:
prompt("sometext","defaultvalue");

JavaScript Functions

To keep the browser from executing a script when the page loads, you can put your script into a function.
A function contains code that will be executed by an event or by a call to that function.
You may call a function from anywhere within the page (or even from other pages if the function is embedded in an external .js file).
Functions can be defined both in the <head> and in the <body> section of a document. However, to assure that the function is read/loaded by the browser before it is called, it could be wise to put it in the <head> section.

Example

<html>
<head>
<script type="text/javascript">
function displaymessage()
{
alert("Hello World!");
}
</script>
</head>
<body>
<form>
<input type="button" value="Click me!"
onclick="displaymessage()" >
</form>
</body>
</html>

If the line: alert("Hello world!!") in the example above had not been put within a function, it would have been executed as soon as the line was loaded. Now, the script is not executed before the user hits the button. We have added an onClick event to the button that will execute the function displaymessage() when the button is clicked.

You will learn more about JavaScript events in the JS Events chapter.

JavaScript Loops

Very often when you write code, you want the same block of code to run over and over again in a row. Instead of adding several almost equal lines in a script we can use loops to perform a task like this.
In JavaScript there are two different kind of loops:
  • for - loops through a block of code a specified number of times
  • while - loops through a block of code while a specified condition is true

The for Loop

The for loop is used when you know in advance how many times the script should run.
Syntax

for (var=startvalue;var<=endvalue;var=var+increment) 
{
    code to be executed
}

Example

Explanation: The example below defines a loop that starts with i=0. The loop will continue to run as long as i is less than, or equal to 10. i will increase by 1 each time the loop runs.
Note: The increment parameter could also be negative, and the <= could be any comparing statement.

<html>
<body>
<script type="text/javascript">
var i=0;
for (i=0;i<=10;i++)
{
document.write("The number is " + i);
document.write("<br />");
}
</script>
</body>
</html>

Result

The number is 0
The number is 1
The number is 2
The number is 3
The number is 4
The number is 5
The number is 6
The number is 7
The number is 8
The number is 9
The number is 10

The while loop

The while loop is used when you want the loop to execute and continue executing while the specified condition is true. 

while (var<=endvalue)
{
    code to be executed
}
Note: The <= could be any comparing statement.

Example

Explanation: The example below defines a loop that starts with i=0. The loop will continue to run as long as i is less than, or equal to 10. i will increase by 1 each time the loop runs.

<html>
<body>
<script type="text/javascript">
var i=0;
while (i<=10)
{
document.write("The number is " + i);
document.write("<br />");
i=i+1;
}
</script>
</body>
</html>

Result

The number is 0
The number is 1
The number is 2
The number is 3
The number is 4
The number is 5
The number is 6
The number is 7
The number is 8
The number is 9
The number is 10

The do...while Loop

The do...while loop is a variant of the while loop. This loop will always execute a block of code ONCE, and then it will repeat the loop as long as the specified condition is true. This loop will always be executed at least once, even if the condition is false, because the code is executed before the condition is tested.

do
{
    code to be executed
}
while (var<=endvalue);

Example

<html>
<body>
<script type="text/javascript">
var i=0;
do 
{
document.write("The number is " + i);
document.write("<br />");
i=i+1;
}
while (i<0);
</script>
</body>
</html>

Result

The number is 0

JavaScript break and continue Statements

There are two special statements that can be used inside loops: break and continue.

Break

The break command will break the loop and continue executing the code that follows after the loop (if any).
Example

<html>
<body>
<script type="text/javascript">
var i=0;
for (i=0;i<=10;i++)
{
if (i==3)
{
break;
}
document.write("The number is " + i);
document.write("<br />");
}
</script>
</body>
</html>

Result

The number is 0
The number is 1
The number is 2

Continue

The continue command will break the current loop and continue with the next value.
Example

<html>
<body>
<script type="text/javascript">
var i=0
for (i=0;i<=10;i++)
{
if (i==3)
{
continue;
}
document.write("The number is " + i);
document.write("<br />");
}
</script>
</body>
</html>

Result

The number is 0
The number is 1
The number is 2
The number is 4
The number is 5
The number is 6
The number is 7
The number is 8
The number is 9
The number is 10

Events

By using JavaScript, we have the ability to create dynamic web pages. Events are actions that can be detected by JavaScript.
Every element on a web page has certain events which can trigger JavaScript functions. For example, we can use the onClick event of a button element to indicate that a function will run when a user clicks on the button. We define the events in the HTML tags.
Examples of events:
  • A mouse click
  • A web page or an image loading
  • Mousing over a hot spot on the web page
  • Selecting an input box in an HTML form
  • Submitting an HTML form
  • A keystroke
Note: Events are normally used in combination with functions, and the function will not be executed before the event occurs!
For a complete reference of the events recognized by JavaScript, go to our complete Event reference.

onload and onUnload

The onload and onUnload events are triggered when the user enters or leaves the page.
The onload event is often used to check the visitor's browser type and browser version, and load the proper version of the web page based on the information.
Both the onload and onUnload events are also often used to deal with cookies that should be set when a user enters or leaves a page. For example, you could have a popup asking for the user's name upon his first arrival to your page. The name is then stored in a cookie. Next time the visitor arrives at your page, you could have another popup saying something like: "Welcome John Doe!".

onFocus, onBlur and onChange

The onFocus, onBlur and onChange events are often used in combination with validation of form fields.
Below is an example of how to use the onChange event. The checkEmail() function will be called whenever the user changes the content of the field:

<input type="text" size="30"
id="email" onchange="checkEmail()">

onSubmit

The onSubmit event is used to validate ALL form fields before submitting it.
Below is an example of how to use the onSubmit event. The checkForm() function will be called when the user clicks the submit button in the form. If the field values are not accepted, the submit should be cancelled. The function checkForm() returns either true or false. If it returns true the form will be submitted, otherwise the submit will be cancelled:

<form method="post" action="xxx.htm"
onsubmit="return checkForm()">

onMouseOver and onMouseOut

onMouseOver and onMouseOut are often used to create "animated" buttons.
Below is an example of an onMouseOver event. An alert box appears when an onMouseOver event is detected:
<a href="http://www.w3schools.com"
onmouseover="alert('An onMouseOver event');return false">
<img src="w3schools.gif" width="100" height="30">
</a>

Object Oriented Programming

JavaScript is an Object Oriented Programming (OOP) language. An OOP language allows you to define your own objects and make your own variable types.
However, creating your own objects will be explained later, in the Advanced JavaScript section. We will start by looking at the built-in JavaScript objects, and how they are used. The next pages will explain each built-in JavaScript object in detail.
Note that an object is just a special kind of data. An object has properties and methods.

Properties

Properties are the values associated with an object.
In the following example we are using the length property of the String object to return the number of characters in a string:

<script type="text/javascript">
var txt="Hello World!";
document.write(txt.length);
</script>

The output of the code above will be:

12

Methods

Methods are the actions that can be performed on objects.
In the following example we are using the toUpperCase() method of the String object to display a text in uppercase letters:

<script type="text/javascript">
var str="Hello world!";
document.write(str.toUpperCase());
</script>

The output of the code above will be:

HELLO WORLD!

String object methods

Method
Description
FF
N
IE
anchor()
Creates an HTML anchor
1
2
3
big()
Displays a string in a big font
1
2
3
blink()
Displays a blinking string
1
2

bold()
Displays a string in bold
1
2
3
charAt()
Returns the character at a specified position
1
2
3
charCodeAt()
Returns the Unicode of the character at a specified position
1
4
4
concat()
Joins two or more strings
1
4
4
fixed()
Displays a string as teletype text
1
2
3
fontcolor()
Displays a string in a specified color
1
2
3
fontsize()
Displays a string in a specified size
1
2
3
fromCharCode()
Takes the specified Unicode values and returns a string
1
4
4
indexOf()
Returns the position of the first occurrence of a specified string value in a string
1
2
3
italics()
Displays a string in italic
1
2
3
lastIndexOf()
Returns the position of the last occurrence of a specified string value, searching backwards from the specified position in a string
1
2
3
link()
Displays a string as a hyperlink
1
2
3
match()
Searches for a specified value in a string
1
4
4
replace()
Replaces some characters with some other characters in a string
1
4
4
search()
Searches a string for a specified value
1
4
4
slice()
Extracts a part of a string and returns the extracted part in a new string
1
4
4
small()
Displays a string in a small font
1
2
3
split()
Splits a string into an array of strings
1
4
4
strike()
Displays a string with a strikethrough
1
2
3
sub()
Displays a string as subscript
1
2
3
substr()
Extracts a specified number of characters in a string, from a start index
1
4
4
substring()
Extracts the characters in a string between two specified indices
1
2
3
sup()
Displays a string as superscript
1
2
3
toLowerCase()
Displays a string in lowercase letters
1
2
3
toUpperCase()
Displays a string in uppercase letters
1
2
3
toSource()
Represents the source code of an object
1
4
-
valueOf()
Returns the primitive value of a String object
1
2
4

String Object Properties

Property
Description
FF
N
IE
constructor
A reference to the function that created the object
1
4
4
length
Returns the number of characters in a string
1
2
3
prototype
Allows you to add properties and methods to the object
1
2
4

JavaScript Date Object Reference

Date Object Methods

FF: Firefox, N: Netscape, IE: Internet Explorer

Method
Description
FF
N
IE
Date()
Returns today's date and time
1
2
3
getDate()
Returns the day of the month from a Date object (from 1-31)
1
2
3
getDay()
Returns the day of the week from a Date object (from 0-6)
1
2
3
getMonth()
Returns the month from a Date object (from 0-11)
1
2
3
getFullYear()
Returns the year, as a four-digit number, from a Date object
1
4
4
getYear()
Returns the year, as a two-digit or a three/four-digit number, depending on the browser. Use getFullYear() instead !!
1
2
3
getHours()
Returns the hour of a Date object (from 0-23)
1
2
3
getMinutes()
Returns the minutes of a Date object (from 0-59)
1
2
3
getSeconds()
Returns the seconds of a Date object (from 0-59)
1
2
3
getMilliseconds()
Returns the milliseconds of a Date object (from 0-999)
1
4
4
getTime()
Returns the number of milliseconds since midnight Jan 1, 1970
1
2
3
getTimezoneOffset()
Returns the difference in minutes between local time and Greenwich Mean Time (GMT)
1
2
3
getUTCDate()
Returns the day of the month from a Date object according to universal time (from 1-31)
1
4
4
getUTCDay()
Returns the day of the week from a Date object according to universal time (from 0-6)
1
4
4
getUTCMonth()
Returns the month from a Date object according to universal time (from 0-11)
1
4
4
getUTCFullYear()
Returns the four-digit year from a Date object according to universal time
1
4
4
getUTCHours()
Returns the hour of a Date object according to universal time (from 0-23)
1
4
4
getUTCMinutes()
Returns the minutes of a Date object according to universal time (from 0-59)
1
4
4
getUTCSeconds()
Returns the seconds of a Date object according to universal time (from 0-59)
1
4
4
getUTCMilliseconds()
Returns the milliseconds of a Date object according to universal time (from 0-999)
1
4
4
parse()
Takes a date string and returns the number of milliseconds since midnight of January 1, 1970
1
2
3
setDate()
Sets the day of the month in a Date object (from 1-31)
1
2
3
setMonth()
Sets the month in a Date object (from 0-11)
1
2
3
setFullYear()
Sets the year in a Date object (four digits)
1
4
4
setYear()
Sets the year in the Date object (two or four digits). Use setFullYear() instead !!
1
2
3
setHours()
Sets the hour in a Date object (from 0-23)
1
2
3
setMinutes()
Set the minutes in a Date object (from 0-59)
1
2
3
setSeconds()
Sets the seconds in a Date object (from 0-59)
1
2
3
setMilliseconds()
Sets the milliseconds in a Date object (from 0-999)
1
4
4
setTime()
Calculates a date and time by adding or subtracting a specified number of milliseconds to/from midnight January 1, 1970
1
2
3
setUTCDate()
Sets the day of the month in a Date object according to universal time (from 1-31)
1
4
4
setUTCMonth()
Sets the month in a Date object according to universal time (from 0-11)
1
4
4
setUTCFullYear()
Sets the year in a Date object according to universal time (four digits)
1
4
4
setUTCHours()
Sets the hour in a Date object according to universal time (from 0-23)
1
4
4
setUTCMinutes()
Set the minutes in a Date object according to universal time (from 0-59)
1
4
4
setUTCSeconds()
Set the seconds in a Date object according to universal time (from 0-59)
1
4
4
setUTCMilliseconds()
Sets the milliseconds in a Date object according to universal time (from 0-999)
1
4
4
toSource()
Represents the source code of an object
1
4
-
toString()
Converts a Date object to a string
1
2
4
toGMTString()
Converts a Date object, according to Greenwich time, to a string. Use toUTCString() instead !!
1
2
3
toUTCString()
Converts a Date object, according to universal time, to a string
1
4
4
toLocaleString()
Converts a Date object, according to local time, to a string
1
2
3
UTC()
Takes a date and returns the number of milliseconds since midnight of January 1, 1970 according to universal time
1
2
3
valueOf()
Returns the primitive value of a Date object
1
2
4

Date Object Properties

Property
Description
FF
N
IE 
constructor
A reference to the function that created the object
1
4
4
prototype
Allows you to add properties and methods to the object



JavaScript RegExp Object


The RegExp object is used to specify what to search for in a text

What is RegExp

RegExp, is short for regular expression.
When you search in a text, you can use a pattern to describe what you are searching for. RegExp IS this 

pattern.

A simple pattern can be a single character.

A more complicated pattern consists of more characters, and can be used for parsing, format checking, substitution and more.
You can specify where in the string to search, what type of characters to search for, and more.

Defining RegExp

The RegExp object is used to store the search pattern.
We define a RegExp object with the new keyword. The following code line defines a RegExp object called patt1 with the pattern "e":

var patt1=new RegExp("e");

When you use this RegExp object to search in a string, you will find the letter "e".

Methods of the RegExp Object

The RegExp Object has 3 methods: test(), exec(), and compile().

test()

The test() method searches a string for a specified value. Returns true or false

Example:

var patt1=new RegExp("e");
document.write(patt1.test("The best things in life are free"));

Since there is an "e" in the string, the output of the code above will be:

true

exec()

The exec() method searches a string for a specified value. Returns the text of the found value. If no match is found, it returns null

Example 1:

var patt1=new RegExp("e");
document.write(patt1.exec("The best things in life are free"));

Since there is an "e" in the string, the output of the code above will be:

e

Example 2:

You can add a second parameter to the RegExp object, to specify your search. For example; if you want to find all occurrences of a character, you can use the "g" parameter ("global").
For a complete list of how to modify your search, visit our complete RegExp object reference.
When using the "g" parameter, the exec() method works like this:
  • Finds the first occurence of "e", and stores its position
  • If you run exec() again, it starts at the stored position, and finds the next occurence of "e", and stores its position 
var patt1=new RegExp("e","g");
do
{
result=patt1.exec("The best things in life are free");
document.write(result);
}
while (result!=null)

Since there is six "e" letters in the string, the output of the code above will be:

eeeeeenull

compile()

The compile() method is used to change the RegExp.
compile() can change both the search pattern, and add or remove the second parameter.

Example:

var patt1=new RegExp("e");
document.write(patt1.test("The best things in life are free"));
patt1.compile("d");
document.write(patt1.test("The best things in life are free"));

Since there is an "e" in the string, but not a "d", the output of the code above will be:

truefalse

Complete RegExp Object Reference

For a complete reference of all the properties and methods that can be used with the RegExp object, go to our complete RegExp object reference.
The reference contains a brief description and examples of use for each property and method including the string object

Java script objects

Date
String
Array
Boolean
Math
RegExp

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