Document Object Model

Designing so that people with disabilities can use a thing, and the standards that make it checkable.

Checking that people using screen readers, keyboards, magnification, or other assistive technology can actually use an interface, through a mix of automated scans and hands-on testing.

Attributes that describe roles, states, and relationships to assistive technology when HTML cannot.

Small programs that modify the browser and the pages it shows, from bookmarklets and userscripts to ad blockers, with access broad enough to make them a standing security risk.

The HTML attribute that makes an element directly editable, and the surface behind most rich-text editors.

Injecting attacker-controlled script into a page that a victim's browser then executes with the victim's own privileges.

Deliberately controlling which element receives keyboard focus as an interface changes.

Confining keyboard focus inside a modal surface so it cannot wander behind it.

The markup language every web page is written in, invented at CERN around 1990 as a simple way to tag documents and link them, and grown by thirty years of browser competition into an application platform.

Attaching client-side behavior to server-rendered markup without rebuilding it.

A whole web page embedded inside another, the web's main isolation boundary for ads, payments, and widgets, and the messaging and sandboxing rules that govern it.

Making every interactive affordance reachable and operable without a pointer.

Any stretch of main-thread work over 50 milliseconds, during which the page can't respond to input, and the techniques for breaking such work up.

Rendering an element into a different part of the document than its logical parent.

Building so the core experience works without scripts, with richer behavior layered on top.

Software that turns an interface into speech or braille for people who can't see the screen, which navigates by structure rather than reading top to bottom, and exposes every shortcut a sighted design took.

Using elements for their meaning, so the document conveys structure without extra description.

A background script the browser runs between a page and the network, able to intercept requests even when no page is open.

An encapsulated DOM subtree whose styles and structure are isolated from the rest of the page.

The nested coordinate system that decides what paints above what, and why z-index often does nothing.

How a front-end application keeps track of the data that changes as people use it, and decides where each piece lives, from local component state to global stores to server caches.

A browser API that animates between two states of a page, or between two pages, by snapshotting the old and new views and morphing between them.

An in-memory representation of the UI that a framework diffs against the previous version to compute minimal real DOM updates.

Rendering only the rows of a long list that are on screen and recycling them as the user scrolls, so a list of a million items costs about as much to display as a list of thirty.

A set of browser-native APIs for building reusable, encapsulated HTML elements without a framework.

A background thread for running JavaScript off the main thread, with no access to the DOM.