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Jumat, 11 April 2014

How to use Javascript localStorage to retain values of HTML input elements on Page Refresh?

How to use Javascript localStorage to retain values of HTML input elements on Page Refresh?

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How to use Javascript localStorage to retain values of HTML input elements on Page Refresh?

localStorage in Javascript is used to retain the values of the HTML input elements on the page refresh. setItem() and getItem() methods are used to set and get the data from the localStorage. clear() method is used to clear the data from the localStorage.

Suppose I have following 2 textboxes and buttons in my HTML page. 

<input type="text" id="text1" value="" />
<button type="button" id="myButton1" onclick="myButtonClicked('text1')">Click Me</button>

<input type="text" id="text2" value="" />
<button type="button" id="myButton2" onclick="myButtonClicked('text2')">Click Me</button>

I fill some data in each textbox. Now when I refresh the page, the data is lost. I want to retain that data on the page refresh. I will use localStorage for this purpose. 

//Store values on button click
function myButtonClicked(id)
{
var aLocalStorage = [];
if(localStorage.getItem('myLocalStorage') != null)
{
aLocalStorage = JSON.parse(localStorage.getItem('myLocalStorage'));
//get stored item from localStorage by json parsing
}
    aLocalStorage.push(id);
    aLocalStorage.push(document.getElementById(id).value);
    localStorage.setItem('myLocalStorage', JSON.stringify(aLocalStorage));
    //stored the entered element id and value in localStorage by doing stringify
}

Now when the page is refresh, call the following function on $(Idocument).ready event like this

$(document).ready(function()
{
retainValues();
});

function retainValues()
{
if(localStorage.getItem('myLocalStorage') != null)
{
var aLocalStorage =[];
aLocalStorage = JSON.parse(localStorage.getItem('myLocalStorage'));

var i = 0;
while (i < aLocalStorage.length)
{   
if (document.getElementById(aLocalStorage[i]) != null)
{
document.getElementById(aLocalStorage[i]).value = shoppingCartList[i+1];
}
i = i + 2;
}
}
}
How to call both Javascript function with PHP file on the click on HTML link?

How to call both Javascript function with PHP file on the click on HTML link?

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How to call both Javascript function with PHP file on the click on HTML link?

Recently, I was trying to implement logout functionality while working with PHP website. I had put logout logic in logout.php file and I was calling that file on the click of logout link like following:

<a href="logout.php">Logout</a>

This was working fine. But later on I realised that I also have to clear localstorage maintained by using Javascript before logging out the user. So, I had to call the javascript function that clears the localstorage before calling the logout.php file. 

Javascript function for clearing the localstorage:

function ClearMyLocalStorage()
{
localStorage.clear();
}

I investigated two approaches to accomplish my task.

Approach 1:

<a href="logout.php" onclick="ClearMyLocalStorage()">

Approach 2:

<a href="javascript:;" onclick="ClearMyLocalStorage();">Logout</a>

And in your function you have to write like

function ClearMyLocalStorage()
{
    localStorage.clear();
    window.location.href = 'logout.php';
}
How to change InnerHTML of all the HTML Buttons in one go using jQuery?

How to change InnerHTML of all the HTML Buttons in one go using jQuery?

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How to change InnerHTML of all the HTML Buttons in one go using jQuery?

Suppose, I have 5 buttons on my page. How can I change the innerHTML of the buttons in one go using jQuery? I want that buttons having text "Clicked" should get changed to "Click me" when Change InnerHTML button is clicked. I will use jQuery to solve this problem. Refer the following example.

<!DOCTYPE html>
<html lang="en">
<head>
<script type="text/javascript">
function ChangeInnerHTML()
{
//Iterate all the buttons with innerHTML = "Clicked" in the DOM and set them to "Click me".
}
</script>
</head>
<body>
<button type="button" id="myButton1">Click me</button>
<button type="button" id="myButton2">Clicked</button>
<button type="button" id="myButton3">Click me</button>
<button type="button" id="myButton4">Clicked</button>
<button type="button" id="myButton5">Click me</button>

<button type="button" id="btnChangeInnerHTML"      onclick="ChangeInnerHTML()">Change InnerHTML</button>

</body>
 </html>

 There are many approaches for doing this task.

Approach 1:

 function ChangeInnerHTML() {
    $('button').each(function() {
        if ($.trim($(this).html()) == "Clicked") 
            $(this).html('Click me');
    });
}

Approach 2:

Use Attribute selector in jquery.

function ChangeInnerHTML() 
{
$("[id^=myButton]:contains('Clicked')").click(function() {
$(this).text("Click Me");

});
}

Approach 3:

function ChangeInnerHTML()
{
document.body.innerHTML=
document.body.innerHTML.replace(/Clicked/g,'Click me');
}

Approach 4:

Without jQuery

function ChangeInnerHTML() 
{
    var btns = document.querySelectorAll('button[id^=myButton]');
    for (var i = 0; i < btns.length; i++) {
        if (btns[i].innerHTML.trim() == 'Clicked') {
            btns[i].innerHTML = 'Click Me'
        }
    }
}

Approach 5:

This will change the innerHTML of all the buttons.

function ChangeInnerHTML()
{
    $("button[id*=myButton]").html("Click me");
}

Jumat, 04 April 2014

How to return value from child window to parent window using window.open in Javascript?

How to return value from child window to parent window using window.open in Javascript?

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How to return value from child window to parent window using window.open in Javascript?

It is very easy to return a value from a child window to parent window which has been opened from parent window using window.open method in Javascript. In many scenarios, it is possible to do some calculations on the child window and parent window need the result of that calculations to perform some task. So, let's try to resolve this problem.

In Parent Window

I have following Javascript function which will open a child window named childWin. I also have a function which will catch the value returned by the child window.

function openChildWin() 
{   
    var childWin = window.open("childWin.html", "_blank", "height=400, width=550, status=yes, toolbar=no, menubar=no, location=no,addressbar=no); 
}

function setValue(val1) 
{
   //you can use the value here which has been returned by your child window
}

ChildWin.html page

Following is my childWin HTML page. There is a button on this HTML page which when clicked will return a value to the parent window which has setValue function. Basically, child window is accessing parent's setValue function here. After this, child window is closed.

<!DOCTYPE html>
<html lang="en">
  <head>

<script type="text/javascript">

function OKClicked()
{
window.opener.setValue('Hello');; //I want to return true here
window.close(); //Close this child window  
}

</script>

  </head>
  <body>
<button type="button" id="OKButton" onclick="OKClicked()">Click ME</button>
  </body>
 </html>

Jumat, 20 Desember 2013

How to allow HTML Textbox to accept Numbers only using Javascript?

How to allow HTML Textbox to accept Numbers only using Javascript?

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How to allow HTML Textbox to accept Numbers only using Javascript?

While web development, you often encounter the need of functionality where your textboxes should be filled with numbers only.

For example, you want your users to fill the quantity of anything, ID (if it is composed on integers only), price of anything (excluding decimal) etc. In short, you want only numbers plus some keys like backspace, delete. left and right arrow to be typed in the textbox. You can use javascript to restrict your users to fill only numbers in the textbox. It is very simple. On the KeyPress event of any HTML text, just call a simple javascript function which checks the keycodes for the numbers and on the basis of keycodes, it returns true or false. Here is how?

HTML Text

<input type="text" id="txtSample" name="txtSample" onkeypress="return CheckNumeric(event)" />

Javascript 

function CheckNumeric(event)
{
       var key = window.event ? event.keyCode : event.which;

        //Check for backspace, delete, left arrow and right arrow keys

if (event.keyCode == 8  || event.keyCode == 46 ||  
           event.keyCode == 37 || event.keyCode == 39) 
{
return true;
}

        //All other keys excluding numeric keys 

else if ( key < 48 || key > 57 ) 
{
return false;
}

else return true; //Numeric keys from 0 to 9
};

Rabu, 27 November 2013

HTML5 MENU Tag Redefined

HTML5 MENU Tag Redefined

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HTML5 <menu> Tag Redefined

The <menu> tag provides an easy way to create menus on a web page. The HTML <menu> element was deprecated in HTML 4.01 but is redefined in HTML5. The HTML <menu> tag defines a list/menu of commands. The <menu> tag is used for context menus, toolbars and for listing form controls and commands.

<li> tag is used within the <menu> tag. For example:

Which pet do you own?
<menu>
 <li>Dog</li>
 <li>Cat</li>
</menu>

You can also place radio buttons and check boxes inside <menu> tags. Have a look at following simple example of <menu> tag

radiobuttons inside <menu> tag

<menu>
   <li><input type="radio" id="radDog" class="radPets" name="radDog"/>Dog</li>
   <li><input type="radio" id="radCat" class="radPets" name="radCat"/>Cat</li>
</menu>

checkboxes inside <menu> tag

<menu>
   <li><input type="checkbox" id="cbDog" class="cbPets" name="cbDog"/>Dog</li>
   <li><input type="checkbox" id="cbCat" class="cbPets" name="cbCat"/>Cat</li>
</menu>

<menu> tag is used instead of <ul> tag

Earlier we used to make an unordered list by using <ul> tag like this:

<ul class="toolbar">
  <li>New</li>
  <li>Open</li>
  <li>Save</li>
  <li>Quit</li>
</ul>

But as I earlier said, <menu> is redefined in HTML5. The <menu> element represents an unordered list of commands. It has a type attribute, which can be set to popup or toolbar.

<menu type="toolbar">
  <li>New</li>
  <li>Open</li>
  <li>Save</li>
  <li>Quit</li>
</menu>

Please note: The <menu> tag is valid within blockquote, body, button, center, dd, div, fieldset, form, iframe, li, noframes, noscript, object, td and th tags.

Sabtu, 23 November 2013

How to secure jQuery AJAX calls in PHP from hackers?

How to secure jQuery AJAX calls in PHP from hackers?

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How to secure jQuery AJAX calls in PHP from hackers?

If you are making jQuery AJAX calls in your PHP website, please ensure that those jQuery AJAX calls are secure from website hackers. Your code should not be vulnerable to hackers. Below are some methods and steps which need to be taken to secure your jQuery AJAX calls to PHP files. I am writing this post because I had written a simple post "How to call PHP function from JavaScript function? Always use AJAX." without mentioning any security code. I got following comment on that post:

"Your code is very vulnerable. You're not filtering the $_POST variable at all. This opens yourself to HTML injection. A hacker could pwn your web site very quickly if you used this code. Careless examples like yours is exactly why so many web sites are hacked."

That's why this is my small attempt to make your jQuery AJAX calls secure. 

1. Use $_SERVER['HTTP_X_REQUESTED_WITH']: 

This is a basic check to see if the request is an Ajax request or not?

if(!empty($_SERVER['HTTP_X_REQUESTED_WITH']) &&       strtolower($_SERVER['HTTP_X_REQUESTED_WITH']) == 'xmlhttprequest') 
{
    //Request identified as ajax request
}

However you should never base your security on this check. It will eliminate direct accesses to the page if that is what you need.

2. Use $_SERVER['HTTP_REFERER']: 

if(@isset($_SERVER['HTTP_REFERER']) && $_SERVER['HTTP_REFERER']=="http://yourdomain/ajaxurl")
{
 //Request identified as ajax request
}

But not all browsers set it. So don't properly rely on it but yes, to some extent it can secure your webpage.

Nobody can AJAX your site from other domain, but always can connect and drieclty send http request, for example by cURL.

JavaScript running on another domain cannot access any page on your domain because this is a violation of the Same-Origin Policy. The attacker would need to exploit an XSS vulnerability in order to pull this off. In short you don't need to worry about this specific attack, just the same old attacks that affect every web application.

3. Generate Access Tokens

$token = md5(rand(1000,9999)); //you can use any encryption
$_SESSION['token'] = $token; //store it as session variable

You can create some token in cookies, that will be also seen from jquery request, but that solution can also be hacked.

4. Always check $_POST variables in your PHP file whether those are set or not? Whether there is valid value in $_POST or not before executing the actual PHP code.

Basic code snippet for securing your jQuery AJAX calls in PHP

Step-1 : Generate Token System For All Web-Service:

Generating Token :

<?php
  session_start();
  $token = md5(rand(1000,9999)); //you can use any encryption
  $_SESSION['token'] = $token; //store it as session variable
?>

Step-2 : Use it while sending ajax call:

var form_data = 
{
  data: $("#data").val(), //your data being sent with ajax
  token:'<?php echo $token; ?>', //used token here.
  is_ajax: 1
};

$.ajax({
  type: "POST",
  url: 'yourajax_url_here',
  data: form_data,
  success: function(response)
  {
    //do further
  }
});

Step-3 : NOW, Let's secure ajax handler PHP file with,

session_start(); 
if($_SERVER['HTTP_X_REQUESTED_WITH'] == 'XMLHttpRequest') 
{
  //Request identified as ajax request

  if(@isset($_SERVER['HTTP_REFERER']) &&    $_SERVER['HTTP_REFERER']=="http://yourdomain/ajaxurl")
  {
   //HTTP_REFERER verification
    if($_POST['token'] == $_SESSION['token']) {
      //do your ajax task
      //don't forget to use sql injection prevention here.
    }
    else
   {
      header('Location: http://yourdomain.com');
    }
  }
  else 
  {
    header('Location: http://yourdomain.com');
  }
}
else 
{
  header('Location: http://yourdomain.com');
}
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