JavaScript glossary: Journeyman level
62 JavaScript terms at the Journeyman level, each with a short definition and a link to its full page.
Updated
- .catch()
- A Promise method that schedules error handling for rejection.
- .then()
- A Promise method that schedules work for successful completion.
- Array Iterator Method
- An Array method that processes items through a callback, such as map, filter, or find.
- async
- A keyword added to functions that allows fetching data in parallel.
- async Function
- A function that always returns a Promise and allows await in its body.
- await
- An operator that pauses an async function until a value or Promise settles.
- catch Block
- A block that handles a matching exception from its try block.
- Class
- A blueprint for making objects that bundle data with actions.
- Class Method
- A function defined as a member of a JavaScript class.
- Closure
- An inner function that remembers the variables around it.
- Constructor
- The special class method that initializes a newly created JavaScript object.
- Custom Error
- An application-specific error class extending JavaScript's Error class.
- Default Export
- The single value a module marks as its default export.
- defer
- A Boolean classic-script attribute that delays execution until parsing finishes while preserving document order.
- Dependency
- External code that a project needs to compile or run.
- Development Dependency
- A package needed for development or testing but not for the application at runtime.
- DOM
- The browser's object representation of an HTML document.
- Encapsulation
- Keeping an object's data behind its methods so it's changed the safe way.
- Error
- An object describing a problem that interrupted normal execution.
- ES Module
- A JavaScript file using import and export to declare dependencies and public values.
- Event
- A member that lets an object notify subscribed code that something happened.
- Event Listener
- A callback registered to run when a particular event occurs.
- every()
- An Array method that reports whether every item passes a test.
- extends
- A keyword that makes one class inherit from another.
- External script
- A script loaded from a separate resource through a script element's src attribute.
- Fetch API
- A browser and runtime API for making HTTP requests that returns a Promise.
- filter()
- Keeps only the items that pass a test.
- finally Block
- A block that normally runs after try and catch whether an exception occurred or not.
- find()
- An Array method that returns the first item satisfying a test.
- Getter
- A method that returns an object's stored value.
- Higher-Order Function
- A function that takes or returns another function.
- Inheritance
- A new class starts with everything from another class, then adds or changes things.
- Inline script
- Script code written directly inside a script element.
- Instance
- One object made from a class, with its own data.
- JSON.parse()
- A method that converts valid JSON text into a JavaScript value.
- JSON.stringify()
- A method that converts a supported JavaScript value into JSON text.
- Lexical Scope
- The rule that a function can use names from where it was written.
- map()
- An Array method that creates a new array by transforming every item.
- Method Overriding
- A child class writing its own version of an inherited method.
- Module script
- A script processed as a JavaScript module with imports, strict mode, and module scoping.
- Named Export
- An exported value imported by its declared export name.
- npm
- The package registry and command-line client commonly used by JavaScript projects.
- Package
- A folder of related modules you can import from.
- package.json
- A project file containing package metadata, scripts, dependencies, and configuration.
- Polymorphism
- Different objects answering the same method call in their own way.
- Private Field
- A class field beginning with # that is accessible only inside its declaring class.
- Promise
- An object representing the eventual fulfillment or rejection of an asynchronous operation.
- Promise State
- A Promise's current state: pending, fulfilled, or rejected.
- Pure Function
- A function that produces the same result for the same inputs without changing outside state.
- querySelector()
- A DOM method that returns the first element matching a CSS selector.
- Recursion
- A function calling itself to solve a smaller piece of the same problem.
- reduce()
- A stream operation that combines elements into one result.
- Response Object
- An object returned by fetch containing an HTTP response's status, headers, and body methods.
- Semantic Versioning
- A major.minor.patch numbering convention communicating compatibility and change size.
- Setter
- A method that validates or changes an object's stored value.
- some()
- An Array method that reports whether at least one item passes a test.
- sort()
- Puts a list in order, changing the list itself.
- Static Import
- An import declaration resolved and loaded as part of a module's dependency graph.
- Static Method
- A class method called on the class itself rather than an instance.
- super
- A reference used to access a superclass constructor or member.
- throw
- A statement that deliberately raises an exception object.
- try Block
- A block containing code that may throw an exception.