JavaScript has three kind of popup boxes: Alert
box, Confirm box, and Prompt box.
When an alert box pops up, the user will have to click "OK" to proceed.
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.
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.
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");
Example
<html>
<head>
<script type="text/javascript">
function show_alert()
{
alert("Hello, I am an alert box!");
}
</script>
</head>
<body>
<input type="button" onclick="show_alert()" value="Show alert box" />
</body>
</html>
<head>
<script type="text/javascript">
function show_alert()
{
alert("Hello, I am an alert box!");
}
</script>
</head>
<body>
<input type="button" onclick="show_alert()" value="Show alert box" />
</body>
</html>
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");
Example
<html>
<head>
<script
type="text/javascript">
function show_confirm()
{
var r=confirm("Press a
button!");
if (r==true)
{
alert("You pressed OK!");
}
else
{
alert("You pressed Cancel!");
}
}
</script>
</head>
<body>
<input type="button"
onclick="show_confirm()" value="Show a confirm box" />
</body>
</html>
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");
Example
<html>
<head>
<script
type="text/javascript">
function show_prompt()
{
var name=prompt("Please enter
your name","Harry Potter");
if (name!=null &&
name!="")
{
document.write("Hello " + name + "! How are you ?");
}
}
</script>
</head>
<body>
<input type="button"
onclick="show_prompt()" value="Show prompt box" />
</body>
</html>
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