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How to use alert(), prompt(), and confirm() in JavaScript

Programming Bytes

In this shot, we will learn about the browser functions alert, prompt, and confirm.

Alert 🚨

alert → It displays a message in an alert box with an OK button. While displaying the alert box, the script execution is paused until the user presses the OK or ESC keys.

Syntax

alert(message)

Example

alert("This is an alert 🚨");

You can also pass in any JavaScript statement:

alert(2+4); //6

Or you can call a function:

function getMessage() {

    return "Hi 👋 from Javascript Jeep ";
}

alert(getMessage())

To display a line break, you can use /n:

alert("Hello from /n JavaScript Jeep");

prompt

The prompt method asks the user to input a value by displaying a dialog with the OK and Cancel buttons. Script execution is paused until the user presses OK or Cancel.

Syntax

let returnValue = prompt(message, [default_value]);

message → The title to display in the dialog box.

default_value → The defaultinitial value of the input box. It is an optional argument in all browsers, except Internet Explorer. In IE (specifically versions 7 and 8), if we don’t pass the default, it will insert “undefined” into the prompt.

The call to prompt returns either the text from the input field or nullif the input was canceled.

const YOB = prompt("What is your Year of Birth?", '');

If the user enters a value and presses OK, then the value stored in the age variable is user input. If the user clicks the Cancel button or Esc key, then the value of age is null.

let YOB = prompt('What is your Year of Birth?', 1900);

const currentYear = new Date().getFullYear();

if(YOB === null) {
    YOB = 1900
}

alert(`You are ${currentYear - YOB} years old!`); // You are 100 years old!

Confirm

The confirm method will display a confirm box that displays a messageusually a question with an OK and Cancel button.

Syntax

let isConfirmed = confirm(question);

The confirm method returns true if OK is pressed; otherwise, it returns false.

Example

let canDelete = confirm("Do you want to delete the file?");

Conclusion

All of these methods pause the script execution and don’t allow the user to interact with the rest of the page until the window is closed.

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