JavaScript Popup Box : Alert Box
- Alert box is used as POPUP box in JavaScript.
- Alert box pops-up with message and ‘OK’ button.
- Alert box have string displayed on it .
- When an alert box pops up, the user will have to click “OK” to proceed.
Syntax :
alert("Sample Text");
- “Sample Text” will be displayed when alert box pops up.
Sample Image of Alert Box
Live Example
<html> <head> <script type="text/javascript"> function show_alert_box() { alert("Hello! This is sample alert box!"); } </script> </head> <body> <input type="button" onclick="show_alert_box()" value="Show alert box"/> </body> </html>
Output
Different Varieties of Alert Box in JavaScript
Verity 1 : Alert box Pops-up when page gets completely loaded
<html> <body> <script type="text/javascript"> alert("Hello world") </script> </body> </html>
Verity 2 : Using Concatenation of Strings and Variable in Alert Box
<html> <body> <script type="text/javascript"> var name = "Pritesh" alert("My name is: " + name) </script> </body> </html>
- “+” is used as concatenation operator.
- “+” Can join two string and variables.
Rule : How to concatenate ?
String + String = String Number + String = String String + Number = String Number + Number = Number
Sample 1 : Number + Number
<script type="text/javascript"> alert(1 + 1) </script>
Output :
Sample 2 : String + Number
<script type="text/javascript"> alert("1" + 1) </script>
Output :
Verity 3 : Javascript alert box that pops-up when a link is clicked
<html> <body> <a href='javascript:onClick = alert("Alert")'>Click Me</a> </body> </html>
- When User Clicks on Link , Alert message will be displayed to the user.
Output :
Click Me
