Posted At: Jul 14, 2024 - 208 Views
Interaction: alert, prompt, confirm
When working in the browser, JavaScript provides several ways to interact with the user. Three commonly used functions are alert, prompt, and confirm.
1. alert
The alert function displays a message to the user in a modal window. The user must click "OK" to proceed.
JavaScript Example:
alert("Hello, welcome to our website!");
TypeScript Example:
alert("Hello, welcome to our website!");
- Description: Displays a modal window with a message.
- Modal Window: The user cannot interact with the rest of the page until the alert is dismissed by clicking "OK".
2. prompt
The prompt function displays a message and requests input from the user. It provides an input field where the user can type a response.
Syntax:
let result = prompt(title, [default]);
let result: string | null = prompt(title, default);
- title: The text to display in the prompt window.
- default: (Optional) The initial value in the input field.
JavaScript Example:
let name = prompt("What is your name?", "Guest");
if (name !== null) {
alert(`Hello, ${name}!`);
} else {
alert("You didn't enter your name.");
}
TypeScript Example:
let name: string | null = prompt("What is your name?", "Guest");
if (name !== null) {
alert(`Hello, ${name}!`);
} else {
alert("You didn't enter your name.");
}
- Behavior: The function returns the text entered by the user or
nullif the user cancels the input.
Note for Internet Explorer:
Always provide a default value to avoid seeing "undefined" in the input field.
Example for IE:
let test = prompt("Test", "");
let test: string | null = prompt("Test", "");
3. confirm
The confirm function displays a message and asks the user to confirm or cancel.
Syntax:
let result = confirm(question);
let result: boolean = confirm(question);
- question: The text to display in the confirm window.
JavaScript Example:
let isBoss = confirm("Are you the boss?");
if (isBoss) {
alert("Welcome, Boss!");
} else {
alert("You are not the boss.");
}
TypeScript Example:
let isBoss: boolean = confirm("Are you the boss?");
if (isBoss) {
alert("Welcome, Boss!");
} else {
alert("You are not the boss.");
}
- Behavior: The function returns
trueif the user clicks "OK" andfalseif the user clicks "Cancel".
Summary
alert
- Usage: To show a message.
- Returns: Nothing.
prompt
- Usage: To get input from the user.
- Returns: The input text or
nullif canceled.
confirm
- Usage: To ask for confirmation.
- Returns:
trueif "OK" is clicked,falseif "Cancel" is clicked.
Important Notes
- Modal Nature: All these functions create modal windows, meaning the user must interact with them before returning to the page.
- Browser Dependent: The exact appearance and placement of these windows depend on the browser and cannot be customized.
Example Use Case
Let's create a simple interaction flow using these functions in both JavaScript and TypeScript:
JavaScript Example:
alert("Welcome to our website!");
let age = prompt("How old are you?", "18");
if (age !== null) {
let isAdult = confirm("Are you sure you are an adult?");
if (isAdult) {
alert("Access granted");
} else {
alert("Access denied");
}
} else {
alert("Please provide your age");
}
TypeScript Example:
alert("Welcome to our website!");
let age: string | null = prompt("How old are you?", "18");
if (age !== null) {
let isAdult: boolean = confirm("Are you sure you are an adult?");
if (isAdult) {
alert("Access granted");
} else {
alert("Access denied");
}
} else {
alert("Please provide your age");
}
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