MohanJava - My Simple JavaScript Tutorial

My Simple JavaScript Tutorial - Examples

This JavaScript tutorial was written in 2003.

JavaScript in Action - Examples

Example: Background Color Change.

The Code:

<form>
    <input type="button" value="Green" name="b1" onClick="document.body.style.backgroundColor='green'">
    <input type="button" value="Red" name="b2" onClick="document.body.style.backgroundColor='red'">
    <input type="button" value="White" name="b3" onClick="document.body.style.backgroundColor='white'">
</form>

Note on HTML "color" attribute values:

For the "color" attribute, we can specify 16 values by the name itself, like white, black, grean, teal, fuchsia, silver ...
For more details: www.w3.org/TR/html4/types.html#h-6.5

Example: Set some text in the brower's status bar.

Place your mouse here and look at the status bar!

The Code:

<a href="http://www.mohanjava.com" target='_blank'
	onMouseover="window.status='World Attractions on your desktop!'; return true"
	onMouseout="window.status=' '; return true">Place your mouse here and look at the status bar!</a>

Example: Browser forward and backward history move.

Note: Will work only if you have any forward or backward history.

The Code:

<form>
	<input type="button" name="b4" value="back" onClick="history.back()">
	<input type="button" name="b5" value="forward" onClick="history.forward()">
</form>

Also like: "history.go(-1)" , "history.go(1)", or "history.go(<number of pages to go back/forward>)"

Example: Alert or Message Box.

Say Hello

The Code:

<form>
    <a href="#" onClick="alert('Hello'); return false;">Say Hello</a>
    </br>
    <input type="button" name="b6" value="Click here" onClick="alert('If a train station is where the train stops, what is a workstation...?!')">
</form>

Example: Getting value from a text box.

The Code:

<form name="myForm">
    <input type="text" name="tx1" value="">
    <input type="button" name="b7" value="Click here" onClick="alert(document.myForm.tx1.value)">
</form>

The syntax is: document.<form name>.<element name>.value

Example: Asking confirmation from the user.

The Code:

<head>
<script language="javascript">
    function makeConfirm() {
        var myAnswer = confirm("Now I am going to format your entire harddisk. Is it OK?");
        if (myAnswer == true) {
            alert("OK. Time to format the harddisk!");
        } else {
            alert("Sorry. You missed a good chance!");
        }
    }
</script>
</head>
<body>
    <form name="myForm">
    <input type="button" name="b8" value="Click here" onClick="javascript:makeConfirm()">
</form>

Example: Get input from user.

The Code:

<head>
    <script language="javascript">
        function askName() {
              var userName= prompt('Please enter your name, so you can get a special greeting', '');
              if (userName == null) {
                  return;
              }

              var guest = '';
              if ((userName == '') || (userName.length == 0)) {
                 guest = "Sorry, you didn't enter any name. I treat you as Guest.";
                 userName = "Guest";
              }

              alert(guest + "Hello " + userName + ", Welcome to My Page!");
        }
    </script>
</head>
<body>
    <form name="myForm">
        <input type="button" name="b9" value="Ask Name" onClick="javascript:askName();">
    </form>
</body>

Example: Show current date and time.

The Code:

<form name="myForm">
    <input type="button" name="b10" value="Show Date" onClick="javascript:alert(new Date())">
</form>

Example: Openning new window with some options.

1. To open a new window with the given width, height, no location, no menu bar, no scroll bar, no status bar. Open new window

2. To open a new window with the given width, height, location, menu bar, scroll bar, status bar. Open new window 2

The Code:

1. To open a new window with the given width, height, no location, no menu bar, no scroll bar, no status bar.

	<A HREF="#"
	onClick="window.open
	('http://www.world-attractions.com',
	'win1',
	'width=500,height=400'); return false;">Open new window</a>

. To open a new window with the given width, height, location, menu bar, scroll bar, status bar.

	<A HREF="#"
	onClick="window.open
	('http://www.mohanjava.com',
	'win2',
	'width=300,height=200,status=yes,menubar=yes,location=yes,scrollbars=yes,resizeable=yes');
	return false;">Open new window 2</a>

Example: Event handling (onClick)

The Code:

<IMG name="coolfan" src="fanoff.gif" width="61" height="72">
<input type="button" value=" Off " onClick="coolfan.src='fanoff.gif'">
<input type="button" value=" On " onClick="coolfan.src='fan.gif'">

Example: Event handling (onMouseOver)

The Code:

<A href="http://www.world-attractions.com/"
onMouseOver="imgfan.src='images/fan.gif'"
onMouseOut="imgfan.src='images/fanoff.gif'"
target="_blank" ><IMG name="imgfan"
src="images/fanoff.gif" width="61" height="72" border="0"></A>

Example: Event handling (onClick and onMouseOver)

Click Me to change the window title. (Look at the window title)

Move your mouse to change window title

The Code:

<a href="#" onClick="document.title='New title by mouse click'; return false;">
Click Me to change the window title.</a>

<a onMouseOver="document.title='New title by mouse over'; return false;">
Move your mouse to change window title</a>

Example: Set focus on a particular form field.

User Name :

Password :

The Code:

<body>
<form name="myForm">
User Name : <input type="text" name="username">
Password  : <input type="password" name="password">
<input type="button" value="Set focus on password field" onClick="document.myForm.password.focus()">
</form>

If suppose want to set the focus at the time of the page loading,

<body onload="document.myForm.username.focus()">

Example: Characters or string manipulation.

Type something (with capital letters):

The Code:

<input type="text" name="textbox1" size="30">
<input type="button" value="Convert to lowercase"
	onClick="document.myForm.textbox1.value=document.myForm.textbox1.value.toLowerCase();">

Example: Number of Characters entered.

The Code:

	<head>
	<script language="javascript">
	<!--
	function setCount(obj1, obj2) {
	    obj2.value = obj1.value.length;
	}
	// -->
	</script>
	</head>
	<body>
	<form name="myForm">
	<TEXTAREA name="tarea" rows="10" cols="30" value=""
	onKeyPress="javascript:setCount(document.myForm.tarea, document.myForm.count);"
	onKeyUp="javascript:setCount(document.myForm.tarea, document.myForm.count);"
	onKeyDown="javascript:setCount(document.myForm.tarea, document.myForm.count);"></TEXTAREA>  
	<input type="text" size="3" name="count">
	</form>

Example: Event handling - onChange.

The Code:

	function openWindow(selectedIndex) {
	    if (selectedIndex == 'Please Select...') {
		return;
	    } else {
		window.open(selectedIndex);
	    }
        }

	<select name="jump" OnChange="openWindow(myForm.jump.options[selectedIndex].value)">
	  <option selected>Please Select...
	  <option value="http://www.world-attractions.com/">world-attractions.com
	  <option value="http://www.mtxis.net/">mtxis.net
	  <option value="http://www.hindumarriage.net/">hindumarriage.net
	</select>

The "window.open(<url>)" will open a new window with this url. But "location.href=<url>" will open this url in the same window.

Example: While Loop Demo

The Code:

	<script language="JavaScript">
	<!--- hide script from old browsers

	function whileLoopdemo() {
	    var askAgain = true;
	    while (askAgain) {
	        answer = prompt("What is the answer for (10 + 5 - 10) ?", 0);
	        if (answer.length == 0) {
		   askAgain = false;
		} else if (answer == 5) {
	    	    alert("Correct. The Answer is 5.");
	            askAgain = false;
		} else {
	            askAgain = confirm("Wrong Answer. Want to try again?");
	        }
	    }
	}
	// stop hiding --->

	</script>

Example: Getting selected value from radio button.

Male Female

The Code:

<script language="JavaScript">
<!--- hide script from old browsers
function getRadioButtonValue(obj) {
    for (i = 0; i < obj.length; i++) {
      if (obj[i].checked) {
          alert("You are selected " + obj[i].value);
      }
   }
}
// stop hiding --->
</script>
<input type="radio" name="radio1" value="Male" onClick="javascript:getRadioButtonValue(document.myForm.radio1);">Male
<input type="radio" name="radio1" value="Female" onClick="javascript:getRadioButtonValue(document.myForm.radio1);">Female

Example: Getting selected values from radio button.

Maths English Science History

The Code:

<script language="JavaScript">
<!--- hide script from old browsers
  function getCheckBoxValue(obj) {
      var message = '';
      for (i = 0; i < obj.length; i++) {
          if (obj[i].checked) {
              message += obj[i].value + ', ';
          }
      }
      if (message == '') {
         message = 'No checkbox selected!';
      }
      alert (message);
}
// stop hiding --->
</script>
<input type="checkbox" name="check1" value="Maths">Maths
<input type="checkbox" name="check1" value="English">English
<input type="checkbox" name="check1" value="Science">Science
<input type="checkbox" name="check1" value="History">History
<input type="button"
value="Get the selected values"
onClick="javascript:getCheckBoxValue(document.myForm.check1);">

Example: Simple Email id validation.

Enter your email :

The Code:

	  <script language="JavaScript">
	  function validateMailId(str) {
	      var errorMsg = 'Invalid mail id';
	      var strLength = str.length
	      if ((str == '') || (strLength == 0)) {
	          alert(errorMsg);
	      } else if ((str.indexOf("@") == -1) || (str.indexOf("@") == 0) || (str.indexOf("@") == (strLength - 1))) {
                  alert(errorMsg);
	      } else if ((str.indexOf(".") == -1) || (str.indexOf(".") == 0) || (str.indexOf(".") == (strLength - 1))) {
                  alert(errorMsg);
	      } else {
                  alert("May be a valid email id");
	      }
	  }
	  </script>
	  Enter your email : <input type="text" name="email">
	  <input type="button" value="Validate Email" onClick="validateMailId(document.myForm.email.value);">

Example: Form fields validation.

* Must fields

* User Id :

* Password :

Email Id :

The Code:

	  <script language="javascript">
	  function validateForm() {
		var str = document.myForm.uId.value;
		if ((str == '') || (str.length == 0)) {
	           alert ("Please enter User Id");
		   document.myForm.uId.focus();
		   return;
		}

	        str = document.myForm.pass.value;
		if ((str == '') || (str.length == 0)) {
	           alert ("Please enter Password");
		   document.myForm.pass.focus();
		   return;
		}

		alert ("Entries OK");
	  }
	  </script>
	<tr><td>* Must fields</td></tr>
      <tr><td>* User Id : <input type="text" name="uId"></td></tr>
      <tr><td>* Password : <input type="password" name="pass"></td></tr>
      <tr><td>Email Id : <input type="text" name="emailId"></td></tr>
      <tr><td><input type="button" value="Validate Form" onClick="validateForm();"></td></tr>