JavaScript glossary: Freelancer level
58 JavaScript terms at the Freelancer level, each with a short definition and a link to its full page.
Updated
- <slot>
- The element that marks where assigned light-DOM content appears inside a shadow tree.
- <template>
- The element that stores inert HTML fragments for later use.
- AbortController
- An object that sends cancellation signals to APIs such as fetch.
- Async Iterator
- An iterator whose next() method returns a Promise for each result.
- Autonomous custom element
- A custom element with its own hyphenated tag name.
- Babel
- A JavaScript compiler commonly used to transform newer syntax for older environments.
- CommonJS
- The Node.js module format based on require() and module.exports.
- Currying
- Transforming a function with several parameters into a sequence of one-parameter functions.
- Custom element
- An author-defined HTML element whose behavior is registered through the Custom Elements API.
- Customized built-in element
- A custom element that extends a built-in HTML element and uses the is attribute.
- Cypress
- A popular in-browser end-to-end testing tool.
- Debounce
- A technique that delays work until rapid calls have stopped for a chosen time.
- Declarative shadow DOM
- HTML syntax that creates a shadow root from a template element during parsing.
- Deep Copy
- A copy of a collection and everything inside it, fully separate.
- Dynamic Import
- The import() expression, which loads a module asynchronously when requested.
- ESLint
- A configurable tool that reports problems and style issues in JavaScript code.
- Event Bubbling
- The phase in which an event moves from its target up through ancestor elements.
- Event Capturing
- The phase in which an event travels from ancestors down toward its target.
- Event Delegation
- Handling events for many descendants with one listener on a shared ancestor.
- Event Object
- An object containing information about an event that occurred.
- Event Target
- The object on which an event was originally dispatched.
- for await...of
- A loop that awaits and visits values from an async iterable.
- Generator Function
- A function declared with function* that can pause and yield several values.
- Immutability
- The practice of creating new values instead of changing existing ones.
- Iterable
- Anything you can loop over with for.
- Iterator
- Gives out items one at a time with next() and remembers where it is.
- Iterator Protocol
- The next() method contract used to produce a sequence of values.
- Local Storage
- Browser key-value storage that remains after the page and browser are closed.
- Map
- A collection that associates unique keys with values.
- Memoization
- Caching a function's result so repeated inputs can return it without recalculation.
- Mock Function
- A test function that records calls and can return controlled values.
- Module Bundler
- A tool that combines a module graph into files prepared for deployment.
- Named slot
- A slot identified by name so matching host children can be assigned to it.
- preventDefault()
- An Event method that cancels the browser's default action when the event is cancelable.
- Promise.all()
- A method returning a Promise that fulfills when every input fulfills or rejects when one rejects.
- Promise.allSettled()
- A method returning results for every input after all have settled.
- Promise.any()
- A method returning the first fulfilled input or rejecting if all inputs reject.
- Promise.race()
- A method returning a Promise that settles when the first input settles.
- Regular Expression
- A pattern for finding or checking text.
- Session Storage
- Browser key-value storage kept for one tab's browsing session.
- Set
- A collection with no duplicates and no set order.
- Shadow host
- An element to which a shadow root is attached.
- Shadow root
- A document fragment that forms the root of a component's encapsulated shadow tree.
- Shallow Copy
- A new collection that still shares the items inside it with the original.
- Slot assignment
- The process that matches a shadow host's children with slots in its shadow tree.
- Source Map
- A file connecting transformed code locations back to the original source.
- stopPropagation()
- An Event method that stops the event from moving to other elements.
- Strict Mode
- A JavaScript mode that rejects some error-prone behavior and changes certain runtime rules.
- structuredClone()
- A function that makes a deep copy of many built-in JavaScript values.
- Symbol
- A primitive whose values are always unique and can be used as object property keys.
- Throttle
- A technique that limits how often repeated calls may run.
- Transpiler
- A tool that converts source code into another version of source code.
- Tree Shaking
- Removing exports that a build can determine are unused.
- Unit Test
- A small automated check of one focused unit of behavior.
- WeakMap
- A Map-like collection with weakly held object or non-registered Symbol keys.
- WeakSet
- A Set-like collection holding objects weakly so it does not prevent garbage collection.
- Web Worker
- A browser worker that runs JavaScript away from the page's main thread.
- yield
- Hands back one value from a generator and pauses until the next one is needed.