A beginner-friendly guide to reading, testing and checking code, including the kind of reply a coding assistant might give. The sample replies on this site were written for the lessons. There is no live AI tool, no account to create, and nothing you type is sent anywhere. Facts are checked against MDN.
MDN calls JavaScript the third layer of the "layer cake" of standard web technologies, after HTML and CSS. MDN: What is JavaScript? On MDN's beginner JavaScript course, HTML is described as the markup language used to structure and give meaning to web content, for example paragraphs, headings, data tables, or embedded images and videos. MDN: What is JavaScript? CSS is a language of style rules used to style HTML content, for example background colours, fonts, and laying content out in more than one column. MDN: What is JavaScript? JavaScript is a scripting language that can create dynamically updating content, control multimedia and animate images. MDN: What is JavaScript?
A simple stack of three layers: HTML for structure, CSS for style, and JavaScript for behaviour. MDN calls this the layer cake of standard web technologies.Drawing: our own, simplified and not to scale
JavaScript is a scripting or programming language that lets you add complex features to web pages, rather than leaving a page as static information to look at. MDN: What is JavaScript? Client-side code runs on the visitor's computer: when a web page is viewed, that code is downloaded, then run and displayed by the browser. MDN: What is JavaScript?
Sample assistant replies
The "assistant" replies on this site were written by us for the lesson. They are not live results from an AI tool, and nothing you type is sent to one. That way every visitor sees the same lesson.
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The AI Literacy Reference Guide
A fact-checked guide to reading, testing and checking code, including what HTML, CSS and JavaScript are, how Array.sort and map(parseInt) can surprise you, and why textContent is safer than innerHTML for plain text.