JavaScript for interactivity in Intro to Computing - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is JavaScript used for in web pages?

JavaScript is used to make web pages interactive. It can respond to user actions like clicks, typing, and mouse movements to change the page without reloading.

beginner

Explain the role of an event listener in JavaScript.

An event listener waits for a specific action (like a click) on a webpage element and then runs a function when that action happens.

beginner

What does the following JavaScript code do?<br>

document.getElementById('btn').addEventListener('click', () => { alert('Hello!'); });

This code waits for a click on the element with id 'btn'. When clicked, it shows a popup message saying 'Hello!'.

beginner

Why is JavaScript called a 'client-side' language?

Because JavaScript runs in the user's web browser (the client), not on the web server. This lets pages react quickly to user actions.

intermediate

How does JavaScript change the content of a web page without reloading it?

JavaScript can change the page by modifying the HTML elements directly using the Document Object Model (DOM), so the page updates instantly.

What does an event listener do in JavaScript?

A Waits for user actions and runs code when they happen

B Loads the web page faster

C Changes the style of the page automatically

D Saves data to the server

An event listener waits for user actions like clicks or typing and runs code when those actions occur.

Which JavaScript method selects an element by its ID?

A document.querySelectorAll()

B document.createElement()

C document.getElementById()

D document.addEventListener()

document.getElementById() selects a single element by its unique ID.

What happens when you run this code?<br>

button.addEventListener('click', () => { console.log('Clicked!'); });

A Shows an alert box

B Changes the button text to 'Clicked!'

C Reloads the page

D Logs 'Clicked!' to the console when the button is clicked

The code logs the message to the browser console when the button is clicked.

Why is JavaScript important for web interactivity?

A It makes pages respond to user actions without reloading

B It styles the page with colors and fonts

C It stores data on the server

D It creates the page layout

JavaScript allows web pages to respond instantly to user actions, improving user experience.

Which of these is NOT a typical use of JavaScript on a web page?

A Animating images or buttons

B Creating the server database

C Changing the page content dynamically

D Validating form input before sending

JavaScript runs in the browser and does not create or manage server databases.

Describe how JavaScript makes a web page interactive using an example.

Think about clicking a button and what happens next.

Explain the role of the Document Object Model (DOM) in JavaScript interactivity.

Imagine the web page as a tree of elements JavaScript can change.