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debrider,
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free premium link generator,
leecher,
linkgen.us,
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Libellés :
JavaScript and Cookies
JavaScript and Cookies
What are Cookies ?
Web Browser and Server use HTTP protocol to communicate and HTTP is a stateless protocol. But for a commercial website it is required to maintain session information among different pages. For example one user registration ends after completing many pages. But how to maintain user's session information across all the web pages.
In many situations, using cookies is the most efficient method of remembering and tracking preferences, purchases, commissions, and other information required for better visitor experience or site statistics.
How It Works ?
Your server sends some data to the visitor's browser in the form of a cookie. The browser may accept the cookie. If it does, it is stored as a plain text record on the visitor's hard drive. Now, when the visitor arrives at another page on your site, the browser sends the same cookie to the server for retrieval. Once retrieved, your server knows/remembers what was stored earlier.
Cookies are a plain text data record of 5 variable-length fields:
- Expires : The date the cookie will expire. If this is blank, the cookie will expire when the visitor quits the browser.
- Domain : The domain name of your site.
- Path : The path to the directory or web page that set the cookie. This may be blank if you want to retrieve the cookie from any directory or page.
- Secure : If this field contains the word "secure" then the cookie may only be retrieved with a secure server. If this field is blank, no such restriction exists.
- Name=Value : Cookies are set and retrieved in the form of key and value pairs.
Cookies were originally designed for CGI programming and cookies' data is automatically transmitted between the web browser and web server, so CGI scripts on the server can read and write cookie values that are stored on the client.
JavaScript can also manipulate cookies using the cookie property of the Document object. JavaScript can read, create, modify, and delete the cookie or cookies that apply to the current web page.
Storing Cookies:
The simplest way to create a cookie is to assign a string value to the document.cookie object, which looks like this:
Syntax:
document.cookie = "key1=value1;key2=value2;expires=date"; |
Here expires attribute is option. If you provide this attribute with a valid date or time then cookie will expire at the given date or time and after that cookies' value will not be accessible.
Note: Cookie values may not include semicolons, commas, or whitespace. For this reason, you may want to use the JavaScript escape() function to encode the value before storing it in the cookie. If you do this, you will also have to use the corresponding unescape() function when you read the cookie value.
Example:
Following is the example to set a customer name in input cookie.
<html>
<head>
<script type="text/javascript">
<!--
function WriteCookie()
{
if( document.myform.customer.value == "" ){
alert("Enter some value!");
return;
}
cookievalue= escape(document.myform.customer.value) + ";";
document.cookie="name=" + cookievalue;
alert("Setting Cookies : " + "name=" + cookievalue );
}
//-->
</script>
</head>
<body>
<form name="myform" action="">
Enter name: <input type="text" name="customer"/>
<input type="button" value="Set Cookie" onclick="WriteCookie();"/>
</form>
</body>
</html>
|
This will produce following result. Now enter something in the text box and press the button "Set Cookie" to set the cookies.
Now your machine has a cookie called name. You can set multiple cookies using multiplekey=value pairs separated by comma.
You will learn how to read this cookie in next section.
Reading Cookies:
Reading a cookie is just as simple as writing one, because the value of the document.cookieobject is the cookie. So you can use this string whenever you want to access the cookie.
The document.cookie string will keep a list of name=value pairs separated by semicolons, wherename is the name of a cookie and value is its string value.
You can use strings' split() function to break the string into key and values as follows:
Example:
Following is the example to get the cookies set in previous section.
<html>
<head>
<script type="text/javascript">
<!--
function ReadCookie()
{
var allcookies = document.cookie;
alert("All Cookies : " + allcookies );
// Get all the cookies pairs in an array
cookiearray = allcookies.split(';');
// Now take key value pair out of this array
for(var i=0; i<cookiearray.length; i++){
name = cookiearray[i].split('=')[0];
value = cookiearray[i].split('=')[1];
alert("Key is : " + name + " and Value is : " + value);
}
}
//-->
</script>
</head>
<body>
<form name="myform" action="">
<input type="button" value="Get Cookie" onclick="ReadCookie()"/>
</form>
</body>
</html>
|
Note: Here length is a method of Array class which returns the length of an array. We will discuss Arrays in a separate chapter. By that time please try to digest it.
This will produce following result. Now press the button "Get Cookie" to see the cookies which you have set in previous section.
Note: There may be some other cookies already set on your machine. So above code will show you all the cookies set at your machine.
Setting the Cookies Expiration Date:
You can extend the life of a cookie beyond the current browser session by setting an expiration date and saving the expiration date within the cookie. This can be done by setting the expiresattribute to a date and time.
Example:
The following example illustrates how to set cookie expiration date after 1 Month :
<html>
<head>
<script type="text/javascript">
<!--
function WriteCookie()
{
var now = new Date();
now.setMonth( now.getMonth() + 1 );
cookievalue = escape(document.myform.customer.value) + ";"
document.cookie="name=" + cookievalue;
document.cookie = "expires=" + now.toUTCString() + ";"
alert("Setting Cookies : " + "name=" + cookievalue );
}
//-->
</script>
</head>
<body>
<form name="formname" action="">
Enter name: <input type="text" name="customer"/>
<input type="button" value="Set Cookie" onclick="WriteCookie()"/>
</form>
</body>
</html>
|
Deleting a Cookie:
Sometimes you will want to delete a cookie so that subsequent attempts to read the cookie return nothing. To do this, you just need to set the expiration date to a time in the past.
Example:
The following example illustrates how to delete cookie by setting expiration date one Month in past :
<html>
<head>
<script type="text/javascript">
<!--
function WriteCookie()
{
var now = new Date();
now.setMonth( now.getMonth() - 1 );
cookievalue = escape(document.myform.customer.value) + ";"
document.cookie="name=" + cookievalue;
document.cookie = "expires=" + now.toUTCString() + ";"
alert("Setting Cookies : " + "name=" + cookievalue );
}
//-->
</script>
</head>
<body>
<form name="formname" action="">
Enter name: <input type="text" name="customer"/>
<input type="button" value="Set Cookie" onclick="WriteCookie()"/>
</form>
</body>
</html>
|
Note: Instead of setting date, you can see new time using setTime() function.
Libellés :
JavaScript Events
JavaScript Events
What is an Event ?
JavaScript's interaction with HTML is handled through events that occur when the user or browser manipulates a page.
When the page loads, that is an event. When the user clicks a button, that click, too, is an event. Another example of events are like pressing any key, closing window, resizing window etc.
Developers can use these events to execute JavaScript coded responses, which cause buttons to close windows, messages to be displayed to users, data to be validated, and virtually any other type of response imaginable to occur.
Events are a part of the Document Object Model (DOM) Level 3 and every HTML element have a certain set of events which can trigger JavaScript Code.
Here we will see few examples to understand a relation between Event and JavaScript:
onclick Event Type:
This is the most frequently used event type which occurs when a user clicks mouse left button. You can put your validation, warning etc against this event type.
Example:
<html>
<head>
<script type="text/javascript">
<!--
function sayHello() {
alert("Hello World")
}
//-->
</script>
</head>
<body>
<input type="button" onclick="sayHello()" value="Say Hello" />
</body>
</html>
|
This will produce following result and when you click Hello button then onclick event will occur which will trigger sayHello() function.
onsubmit event type:
Another most important event type is onsubmit. This event occurs when you try to submit a form. So you can put your form validation against this event type.
Here is simple example showing its usage. Here we are calling a validate() function before submitting a form data to the webserver. If validate() function returns true the form will be submitted otherwise it will not submit the data.
Example:
<html>
<head>
<script type="text/javascript">
<!--
function validation() {
all validation goes here
.........
return either true or false
}
//-->
</script>
</head>
<body>
<form method="POST" action="t.cgi" onsubmit="return validate()">
.......
<input type="submit" value="Submit" />
</form>
</body>
</html>
|
onmouseover and onmouseout:
These two event types will help you to create nice effects with images or even with text as well. The onmouseover event occurs when you bring your mouse over any element and theonmouseout occurs when you take your mouse out from that element.
Example:
Following example shows how a division reacts when we bring our mouse in that division:
<html>
<head>
<script type="text/javascript">
<!--
function over() {
alert("Mouse Over");
}
function out() {
alert("Mouse Out");
}
//-->
</script>
</head>
<body>
<div onmouseover="over()" onmouseout="out()">
<h2> This is inside the division </h2>
</div>
</body>
</html>
|
You can change different images using these two event types or you can create help baloon to help your users.
HTML 4 Standard Events
The standard HTML 4 events are listed here for your reference. Here script indicates a Javascript function to be executed agains that event.
| Event | Value | Description |
|---|---|---|
| onchange | script | Script runs when the element changes |
| onsubmit | script | Script runs when the form is submitted |
| onreset | script | Script runs when the form is reset |
| onselect | script | Script runs when the element is selected |
| onblur | script | Script runs when the element loses focus |
| onfocus | script | Script runs when the element gets focus |
| onkeydown | script | Script runs when key is pressed |
| onkeypress | script | Script runs when key is pressed and released |
| onkeyup | script | Script runs when key is released |
| onclick | script | Script runs when a mouse click |
| ondblclick | script | Script runs when a mouse double-click |
| onmousedown | script | Script runs when mouse button is pressed |
| onmousemove | script | Script runs when mouse pointer moves |
| onmouseout | script | Script runs when mouse pointer moves out of an element |
| onmouseover | script | Script runs when mouse pointer moves over an element |
| onmouseup | script | Script runs when mouse button is released |
Libellés :
JavaScript Functions
JavaScript Functions
A function is a group of reusable code which can be called anywhere in your programme. This eliminates the need of writing same code again and again. This will help programmers to write modular code. You can divide your big programme in a number of small and manageable functions.
Like any other advance programming language, JavaScript also supports all the features necessary to write modular code using functions.
You must have seen functions like alert() and write() in previous chapters. We are using these function again and again but they have been written in core JavaScript only once.
JavaScript allows us to write our own functions as well. This section will explain you how to write your own functions in JavaScript.
Function Definition:
Before we use a function we need to define that function. The most common way to define a function in JavaScript is by using the function keyword, followed by a unique function name, a list of parameters (that might be empty), and a statement block surrounded by curly braces. The basic syntax is shown here:
<script type="text/javascript">
<!--
function functionname(parameter-list)
{
statements
}
//-->
</script>
|
Example:
A simple function that takes no parameters called sayHello is defined here:
<script type="text/javascript">
<!--
function sayHello()
{
alert("Hello there");
}
//-->
</script>
|
Calling a Function:
To invoke a function somewhere later in the script, you would simple need to write the name of that function as follows:
<script type="text/javascript"> <!-- sayHello(); //--> </script> |
Function Parameters:
Till now we have seen function without a parameters. But there is a facility to pass different parameters while calling a function. These passed parameters can be captured inside the function and any manipulation can be done over those parameters.
A function can take multiple parameters separated by comma.
Example:
Let us do a bit modification in our sayHello function. This time it will take two parameters:
<script type="text/javascript">
<!--
function sayHello(name, age)
{
alert( name + " is " + age + " years old.");
}
//-->
</script>
|
Note: We are using + operator to concatenate string and number all together. JavaScript does not mind in adding numbers into strings.
Now we can call this function as follows:
<script type="text/javascript">
<!--
sayHello('Zara', 7 );
//-->
</script>
|
The return Statement:
A JavaScript function can have an optional return statement. This is required if you want to return a value from a function. This statement should be the last statement in a function.
For example you can pass two numbers in a function and then you can expect from the function to return their multiplication in your calling program.
Example:
This function takes two parameters and concatenates them and return resultant in the calling program:
<script type="text/javascript">
<!--
function concatenate(first, last)
{
var full;
full = first + last;
return full;
}
//-->
</script>
|
Now we can call this function as follows:
<script type="text/javascript">
<!--
var result;
result = concatenate('Zara', 'Ali');
alert(result );
//-->
</script>
|
Libellés :
JavaScript Loop Control
JavaScript Loop Control
JavaScript provides you full control to handle your loops and switch statement. There may be a situation when you need to come out of a loop without reaching at its bottom. There may also be a situation when you want to skip a part of your code block and want to start next iteration of the look.
To handle all such situations, JavaScript provides break and continue statements. These statements are used to immediately come out of any loop or to start the next iteration of any loop respectively.
The break Statement:
The break statement, which was briefly introduced with the switch statement, is used to exit a loop early, breaking out of the enclosing curly braces.
Example:
This example illustrates the use of a break statement with a while loop. Notice how the loop breaks out early once x reaches 5 and reaches to document.write(..) statement just below to closing curly brace:
<script type="text/javascript">
<!--
var x = 1;
document.write("Entering the loop<br /> ");
while (x < 20)
{
if (x == 5){
break; // breaks out of loop completely
}
x = x + 1;
document.write( x + "<br />");
}
document.write("Exiting the loop!<br /> ");
//-->
</script>
|
This will produce following result:
Entering the loop 2 3 4 5 Exiting the loop! |
We already have seen the usage of break statement inside a switch statement.
The continue Statement:
The continue statement tells the interpreter to immediately start the next iteration of the loop and skip remaining code block.
When a continue statement is encountered, program flow will move to the loop check expression immediately and if condition remain true then it start next iteration otherwise control comes out of the loop.
Example:
This example illustrates the use of a continue statement with a while loop. Notice how thecontinue statement is used to skip printing when the index held in variable x reaches 5:
<script type="text/javascript">
<!--
var x = 1;
document.write("Entering the loop<br /> ");
while (x < 10)
{
x = x + 1;
if (x == 5){
continue; // skill rest of the loop body
}
document.write( x + "<br />");
}
document.write("Exiting the loop!<br /> ");
//-->
</script>
|
This will produce following result:
Entering the loop 2 3 4 6 7 8 9 10 Exiting the loop! |
Using Labels to Control the Flow:
Starting from JavaScript 1.2, a label can be used with break and continue to control the flow more precisely.
A label is simply an identifier followed by a colon that is applied to a statement or block of code. We will see two different examples to understand label with break and continue.
Note: Line breaks are not allowed between the continue or break statement and its label name. Also, there should not be any other statement in between a label name and associated loop.
Example 1:
<script type="text/javascript">
<!--
document.write("Entering the loop!<br /> ");
outerloop: // This is the label name
for (var i = 0; i < 5; i++)
{
document.write("Outerloop: " + i + "<br />");
innerloop:
for (var j = 0; j < 5; j++)
{
if (j > 3 ) break ; // Quit the innermost loop
if (i == 2) break innerloop; // Do the same thing
if (i == 4) break outerloop; // Quit the outer loop
document.write("Innerloop: " + j + " <br />");
}
}
document.write("Exiting the loop!<br /> ");
//-->
</script>
|
This will produce following result:
Entering the loop! Outerloop: 0 Innerloop: 0 Innerloop: 1 Innerloop: 2 Innerloop: 3 Outerloop: 1 Innerloop: 0 Innerloop: 1 Innerloop: 2 Innerloop: 3 Outerloop: 2 Outerloop: 3 Innerloop: 0 Innerloop: 1 Innerloop: 2 Innerloop: 3 Outerloop: 4 Exiting the loop! |
Example 2:
<script type="text/javascript">
<!--
document.write("Entering the loop!<br /> ");
outerloop: // This is the label name
for (var i = 0; i < 3; i++)
{
document.write("Outerloop: " + i + "<br />");
for (var j = 0; j < 5; j++)
{
if (j == 3){
continue outerloop;
}
document.write("Innerloop: " + j + "<br />");
}
}
document.write("Exiting the loop!<br /> ");
//-->
</script>
|
This will produce following result:
Entering the loop! Outerloop: 0 Innerloop: 0 Innerloop: 1 Innerloop: 2 Outerloop: 1 Innerloop: 0 Innerloop: 1 Innerloop: 2 Outerloop: 2 Innerloop: 0 Innerloop: 1 Innerloop: 2 Exiting the loop! |
Libellés :
JavaScript for...in loop
JavaScript for...in loop
There is one more loop supported by JavaScript. It is called for...in loop. This loop is used to loop through an object's properties.
Because we have not discussed Objects yet, so you may not feel comfortable with this loop. But once you will have understanding on JavaScript objects then you will find this loop very useful.
Syntax:
for (variablename in object){
statement or block to execute
}
|
In each iteration one property from object is assigned to variablename and this loop continues till all the properties of the object are exhausted.
Example:
Here is the following example that prints out the properties of a Web browser's Navigatorobject:
<script type="text/javascript">
<!--
var aProperty;
document.write("Navigator Object Properties<br /> ");
for (aProperty in navigator)
{
document.write(aProperty);
document.write("<br />");
}
document.write("Exiting from the loop!");
//-->
</script>
|
This will produce following result:
Navigator Object Properties appCodeName appName appMinorVersion cpuClass platform plugins opsProfile userProfile systemLanguage userLanguage appVersion userAgent onLine cookieEnabled mimeTypes Exiting from the loop! |
Libellés :
JavaScript for Loops
JavaScript for Loops
We have seen different variants of while loop. This chapter will explain another popular loop called for loop.
The for Loop
The for loop is the most compact form of looping and includes the following three important parts:
- The loop initialization where we initialize our counter to a starting value. The initialization statement is executed before the loop begins.
- The test statement which will test if the given condition is true or not. If condition is true then code given inside the loop will be executed otherwise loop will come out.
- The iteration statement where you can increase or decrease your counter.
You can put all the three parts in a single line separated by a semicolon.
Syntax:
for (initialization; test condition; iteration statement){
Statement(s) to be executed if test condition is true
}
|
Example:
Following example illustrates a basic for loop:
<script type="text/javascript">
<!--
var count;
document.write("Starting Loop" + "<br />");
for(count = 0; count < 10; count++){
document.write("Current Count : " + count );
document.write("<br />");
}
document.write("Loop stopped!");
//-->
</script>
|
This will produce following result which is similar to while loop:
Starting Loop Current Count : 0 Current Count : 1 Current Count : 2 Current Count : 3 Current Count : 4 Current Count : 5 Current Count : 6 Current Count : 7 Current Count : 8 Current Count : 9 Loop stopped! |
Libellés :
JavaScript while Loops
JavaScript while Loops
While writing a program, there may be a situation when you need to perform some action over and over again. In such situation you would need to write loop statements to reduce the number of lines.
JavaScript supports all the necessary loops to help you on all steps of programming.
The while Loop
The most basic loop in JavaScript is the while loop which would be discussed in this tutorial.
Syntax:
while (expression){
Statement(s) to be executed if expression is true
}
|
The purpose of a while loop is to execute a statement or code block repeatedly as long asexpression is true. Once expression becomes false, the loop will be exited.
Example:
Following example illustrates a basic while loop:
<script type="text/javascript">
<!--
var count = 0;
document.write("Starting Loop" + "<br />");
while (count < 10){
document.write("Current Count : " + count + "<br />");
count++;
}
document.write("Loop stopped!");
//-->
</script>
|
This will produce following result:
Starting Loop Current Count : 0 Current Count : 1 Current Count : 2 Current Count : 3 Current Count : 4 Current Count : 5 Current Count : 6 Current Count : 7 Current Count : 8 Current Count : 9 Loop stopped! |
The do...while Loop:
The do...while loop is similar to the while loop except that the condition check happens at the end of the loop. This means that the loop will always be executed at least once, even if the condition is false.
Syntax:
do{
Statement(s) to be executed;
} while (expression);
|
Note the semicolon used at the end of the do...while loop.
Example:
Let us write above example in terms of do...while loop.
<script type="text/javascript">
<!--
var count = 0;
document.write("Starting Loop" + "<br />");
do{
document.write("Current Count : " + count + "<br />");
count++;
}while (count < 0);
document.write("Loop stopped!");
//-->
</script>
|
This will produce following result:
Starting Loop Current Count : 0 Loop stopped! |
Libellés :
JavaScript Switch Case
JavaScript Switch Case
You can use multiple if...else if statements, as in the previous chapter, to perform a multiway branch. However, this is not always the best solution, especially when all of the branches depend on the value of a single variable.
Starting with JavaScript 1.2, you can use a switch statement which handles exactly this situation, and it does so more efficiently than repeated if...else if statements.
Syntax:
The basic syntax of the switch statement is to give an expression to evaluate and several different statements to execute based on the value of the expression. The interpreter checks each case against the value of the expression until a match is found. If nothing matches, adefault condition will be used.
switch (expression)
{
case condition 1: statement(s)
break;
case condition 2: statement(s)
break;
...
case condition n: statement(s)
break;
default: statement(s)
}
|
The break statements indicate to the interpreter the end of that particular case. If they were omitted, the interpreter would continue executing each statement in each of the following cases.
We will explain break statement in Loop Control chapter.
Example:
Following example illustrates a basic while loop:
<script type="text/javascript">
<!--
var grade='A';
document.write("Entering switch block<br />");
switch (grade)
{
case 'A': document.write("Good job<br />");
break;
case 'B': document.write("Pretty good<br />");
break;
case 'C': document.write("Passed<br />");
break;
case 'D': document.write("Not so good<br />");
break;
case 'F': document.write("Failed<br />");
break;
default: document.write("Unknown grade<br />")
}
document.write("Exiting switch block");
//-->
</script>
|
This will produce following result:
Entering switch block Good job Exiting switch block |
Example:
Consider a case if you do not use break statement:
<script type="text/javascript">
<!--
var grade='A';
document.write("Entering switch block<br />");
switch (grade)
{
case 'A': document.write("Good job<br />");
case 'B': document.write("Pretty good<br />");
case 'C': document.write("Passed<br />");
case 'D': document.write("Not so good<br />");
case 'F': document.write("Failed<br />");
default: document.write("Unknown grade<br />")
}
document.write("Exiting switch block");
//-->
</script>
|
This will produce following result:
Entering switch block Good job Pretty good Passed Not so good Failed Unknown grade Exiting switch block |
Libellés :
JavaScript if...else Statements
JavaScript if...else Statements
While writing a program, there may be a situation when you need to adopt one path out of the given two paths. So you need to make use of conditional statements that allow your program to make correct decisions and perform right actions.
JavaScript supports conditional statements which are used to perform different actions based on different conditions. Here we will explain if..else statement.
JavaScript supports following forms of if..else statement:
- if statement
- if...else statement
- if...else if... statement.
if statement:
The if statement is the fundamental control statement that allows JavaScript to make decisions and execute statements conditionally.
Syntax:
if (expression){
Statement(s) to be executed if expression is true
}
|
Here JavaScript expression is evaluated. If the resulting value is true, given statement(s) are executed. If expression is false then no statement would be not executed. Most of the times you will use comparison operators while making decisions.
Example:
<script type="text/javascript">
<!--
var age = 20;
if( age > 18 ){
document.write("<b>Qualifies for driving</b>");
}
//-->
</script>
|
This will produce following result:
Qualifies for driving |
if...else statement:
The if...else statement is the next form of control statement that allows JavaScript to execute statements in more controlled way.
Syntax:
if (expression){
Statement(s) to be executed if expression is true
}else{
Statement(s) to be executed if expression is false
}
|
Here JavaScript expression is evaluated. If the resulting value is true, given statement(s) in theif block, are executed. If expression is false then given statement(s) in the else block, are executed.
Example:
<script type="text/javascript">
<!--
var age = 15;
if( age > 18 ){
document.write("<b>Qualifies for driving</b>");
}else{
document.write("<b>Does not qualify for driving</b>");
}
//-->
</script>
|
This will produce following result:
Does not qualify for driving |
if...else if... statement:
The if...else if... statement is the one level advance form of control statement that allows JavaScript to make correct decision out of several conditions.
Syntax:
if (expression 1){
Statement(s) to be executed if expression 1 is true
}else if (expression 2){
Statement(s) to be executed if expression 2 is true
}else if (expression 3){
Statement(s) to be executed if expression 3 is true
}else{
Statement(s) to be executed if no expression is true
}
|
There is nothing special about this code. It is just a series of if statements, where each if is part of the else clause of the previous statement. Statement(s) are executed based on the true condition, if non of the condition is true then else block is executed.
Example:
<script type="text/javascript">
<!--
var book = "maths";
if( book == "history" ){
document.write("<b>History Book</b>");
}else if( book == "maths" ){
document.write("<b>Maths Book</b>");
}else if( book == "economics" ){
document.write("<b>Economics Book</b>");
}else{
document.write("<b>Unknown Book</b>");
}
//-->
</script>
|
This will produce following result:
Maths Book |
Libellés :
JavaScript Operators
JavaScript Operators
What is an operator?
Simple answer can be given using expression 4 + 5 is equal to 9. Here 4 and 5 are called operands and + is called operator. JavaScript language supports following type of operators.
- Arithmetic Operators
- Comparision Operators
- Logical (or Relational) Operators
- Assignment Operators
- Conditional (or ternary) Operators
Lets have a look on all operators one by one.
The Arithmatic Operators:
There are following arithmatic operators supported by JavaScript language:
Assume variable A holds 10 and variable B holds 20 then:
| Operator | Description | Example |
|---|---|---|
| + | Adds two operands | A + B will give 30 |
| - | Subtracts second operand from the first | A - B will give -10 |
| * | Multiply both operands | A * B will give 200 |
| / | Divide numerator by denumerator | B / A will give 2 |
| % | Modulus Operator and remainder of after an integer division | B % A will give 0 |
| ++ | Increment operator, increases integer value by one | A++ will give 11 |
| -- | Decrement operator, decreases integer value by one | A-- will give 9 |
Note: Addition operator (+) works for Numeric as well as Strings. e.g. "a" + 10 will give "a10".
The Comparison Operators:
There are following comparison operators supported by JavaScript language
Assume variable A holds 10 and variable B holds 20 then:
| Operator | Description | Example |
|---|---|---|
| == | Checks if the value of two operands are equal or not, if yes then condition becomes true. | (A == B) is not true. |
| != | Checks if the value of two operands are equal or not, if values are not equal then condition becomes true. | (A != B) is true. |
| > | Checks if the value of left operand is greater than the value of right operand, if yes then condition becomes true. | (A > B) is not true. |
| < | Checks if the value of left operand is less than the value of right operand, if yes then condition becomes true. | (A < B) is true. |
| >= | Checks if the value of left operand is greater than or equal to the value of right operand, if yes then condition becomes true. | (A >= B) is not true. |
| <= | Checks if the value of left operand is less than or equal to the value of right operand, if yes then condition becomes true. | (A <= B) is true. |
The Logical Operators:
There are following logical operators supported by JavaScript language
Assume variable A holds 10 and variable B holds 20 then:
| Operator | Description | Example |
|---|---|---|
| && | Called Logical AND operator. If both the operands are non zero then then condition becomes true. | (A && B) is true. |
| || | Called Logical OR Operator. If any of the two operands are non zero then then condition becomes true. | (A || B) is true. |
| ! | Called Logical NOT Operator. Use to reverses the logical state of its operand. If a condition is true then Logical NOT operator will make false. | !(A && B) is false. |
The Bitwise Operators:
There are following bitwise operators supported by JavaScript language
Assume variable A holds 2 and variable B holds 3 then:
| Operator | Description | Example |
|---|---|---|
| & | Called Bitwise AND operator. It performs a Boolean AND operation on each bit of its integer arguments. | (A & B) is 2 . |
| | | Called Bitwise OR Operator. It performs a Boolean OR operation on each bit of its integer arguments. | (A | B) is 3. |
| ^ | Called Bitwise XOR Operator. It performs a Boolean exclusive OR operation on each bit of its integer arguments. Exclusive OR means that either operand one is true or operand two is true, but not both. | (A ^ B) is 1. |
| ~ | Called Bitwise NOT Operator. It is a is a unary operator and operates by reversing all bits in the operand. | (~B) is -4 . |
| << | Called Bitwise Shift Left Operator. It moves all bits in its first operand to the left by the number of places specified in the second operand. New bits are filled with zeros. Shifting a value left by one position is equivalent to multiplying by 2, shifting two positions is equivalent to multiplying by 4, etc. | (A << 1) is 4. |
| >> | Called Bitwise Shift Right with Sign Operator. It moves all bits in its first operand to the right by the number of places specified in the second operand. The bits filled in on the left depend on the sign bit of the original operand, in order to preserve the sign of the result. If the first operand is positive, the result has zeros placed in the high bits; if the first operand is negative, the result has ones placed in the high bits. Shifting a value right one place is equivalent to dividing by 2 (discarding the remainder), shifting right two places is equivalent to integer division by 4, and so on. | (A >> 1) is 1. |
| >>> | Called Bitwise Shift Right with Zero Operator. This operator is just like the >> operator, except that the bits shifted in on the left are always zero, | (A >>> 1) is 1. |
The Assignment Operators:
There are following assignment operators supported by JavaScript language:
| Operator | Description | Example |
|---|---|---|
| = | Simple assignment operator, Assigns values from right side operands to left side operand | C = A + B will assigne value of A + B into C |
| += | Add AND assignment operator, It adds right operand to the left operand and assign the result to left operand | C += A is equivalent to C = C + A |
| -= | Subtract AND assignment operator, It subtracts right operand from the left operand and assign the result to left operand | C -= A is equivalent to C = C - A |
| *= | Multiply AND assignment operator, It multiplies right operand with the left operand and assign the result to left operand | C *= A is equivalent to C = C * A |
| /= | Divide AND assignment operator, It divides left operand with the right operand and assign the result to left operand | C /= A is equivalent to C = C / A |
| %= | Modulus AND assignment operator, It takes modulus using two operands and assign the result to left operand | C %= A is equivalent to C = C % A |
Note: Same logic applies to Bitwise operators so they will become like <<=, >>=, >>=, &=, |= and ^=.
Miscellaneous Operator
The Conditional Operator (? :)
There is an oprator called conditional operator. This first evaluates an expression for a true or false value and then execute one of the two given statements depending upon the result of the evaluation. The conditioanl operator has this syntax:
| Operator | Description | Example |
|---|---|---|
| ? : | Conditional Expression | If Condition is true ? Then value X : Otherwise value Y |
The typeof Operator
The typeof is a unary operator that is placed before its single operand, which can be of any type. Its value is a string indicating the data type of the operand.
The typeof operator evaluates to "number", "string", or "boolean" if its operand is a number, string, or boolean value and returns true or false based on the evaluation.
Here is the list of return values for the typeof Operator :
| Type | String Returned by typeof |
|---|---|
| Number | "number" |
| String | "string" |
| Boolean | "boolean" |
| Object | "object" |
| Function | "function" |
| Undefined | "undefined" |
| Null | "object" |
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