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Alerts In Javascript

In this tutorial we will talk about alerts in JavaScript. Alerts in JavaScript are used to give some information to the user or to get some information from the user. There are three types of alerts in JavaScript

Alert box
Confirm box
Prompt box

Alert Box

This alert is used to give some information to the client like show error message if something is wrongly entered by the user, display a confirmation message and so on.

Syntax

alert("<message>");

Example

alert("Hi,this message is for information purpose.");

Output

Picture showing the alert box in JavaScript

Click to Enlarge

Confirm Box

This alert is mainly used if it is required to get yes-no confirmation from the user. For example, if the user is saving value in the database, then it is always good to confirm it from the user if he really wants to save the value.

Syntax

if (confirm("<confirmation_message>") == true) {
            // Do Something
}
else {
                // Do something else
}

Confirm box returns a Boolean value depends upon the option selected by the user. If the user selects Yes then returns true else false.

Example

if(confirm("Are you sure you want to save your personal information?") == true) {
        // Do Something
}
else{
        // Do Something else
}

Output

Picture showing the confirm box in JavaScript

Click to Enlarge

Prompt Box

Prompt box is required in the scenario in which you want some input from the user. Let us consider a system in which requires the system to enter the age of the person and based on which it gives information whether the user is eligible for the vote or not.

Syntax

var variable_name = prompt("<message>","<default_string>");

Example

var age = prompt("Please enter your age", "18");
 if (parseInt(age) >= 18) {
  alert("You are eligible to vote");
 } else {
  alert("Sorry,you can't vote");
 }

Everything is clear in the above code but there is one thing that needs attention i.e. parseInt. This function converts object into integer.

Output

Picture showing the prompt box in JavaScript

Click to Enlarge

If the user clicks ok then value 18 is assigned in variable age else null. So be careful in handling the value when you are using prompt box.

Posted By -	Karan Gupta

Posted On -	Tuesday, March 22, 2011

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