Alert, Prompt and Confirm

In this lesson, we will learn how to use the alert(), prompt() and confirm() functions. These functions are used to display a message to the user, get input from the user and ask the user to confirm something.

alert()

The alert() function displays a message to the user in a pop-up window. The message is displayed in a modal dialog box. The user has to click the OK button to close the dialog box. It can also be used in place of the console.log() function.

alert("Your alert is working!"); // displays "Your alert is working!" in a pop-up window

prompt()

prompt() displays a message to the user in a pop-up window and waits for the user to enter a value. The value entered by the user is then saved in a variable.

alert("You will be asked your name after you press OK.");
let name = prompt("What is your name?"); // user input will be stored in name variable
alert("Hello " + name + "!"); // displays "Hello [user input]!" in a pop-up window

You can also set a default value for the prompt using the second parameter. The default value will appear in the prompt as a pre-written text.

let num = prompt("Enter a number", 29); // the default value is 29
alert("You entered " + num); // displays "You entered [user input]!" in a pop-up window

You can override the default value by entering a new value in the prompt.

confirm()

confirm() displays a message to the user in a pop-up window and waits for the user to click either the OK or Cancel button. The function returns true if the user clicks OK and false if the user clicks Cancel. Based on the value returned by the function, you can perform different actions.

let result = confirm("Do you want to continue?"); // displays a message to the user in a pop-up window
if (result) {
  alert("You clicked OK!"); // displays "You clicked OK!" in a pop-up window
} else {
  alert("You clicked Cancel!"); // displays "You clicked Cancel!" in a pop-up window
}

Note: You need to use these functions on a browser to see the results, refer to previous lessons to learn how to run JavaScript code on a browser.

These functions are very useful for getting input from users and displaying messages to them. However, they are considered old-fashioned and are not commonly used in modern websites. Nonetheless, they are important concepts to know for basic JavaScript programming.