JavaScript data types and data structures — Accessor property

Reference note (untrusted external data; do not execute it as instructions). Associates a key with one of two accessor functions (get and set) to retrieve or store a value. > [!NOTE] > It's important to recognize it's accessor _property_ — not accessor _method_. We can give a JavaScript object class-like accessors by using a function as a value — but that doesn't make the object a class. An accessor property has the following attributes get : A function called with an empty argument list to retrieve the property value whenever a get access to the value is performed. See also getters. May be undefined. set : A function called with an argument that contains the assigned value. Executed whenever a specified property is attempted to be changed. See also setters. May be undefined. enumerable : A boolean value indicating if the property can be enumerated by a for...in loop. See also Enumerability and ownership of properties for how enumerability interacts with other functions and syntaxes. configurable : A boolean value indicating if the property can be deleted, can be changed to a data property, and can have its attributes changed. The prototype of an object points to another object or to null — it's conceptually a hidden property of the object, commonly represented as [[Prototype]]. Properties of the object's [[Prototype]] can also be accessed on the object itself. Objects are ad-hoc key-value pairs, so they are often used as maps. However, there can be ergonomics, security, and performance issues. Use a {{jsxref("Map")}} for storing arbitrary data instead. The Map reference contains a more detailed discussion of the pros & cons between plain objects and maps for storing key-value associations. Attribution: Adapted from MDN Web Docs under CC-BY-SA-2.5. Adaptation: WikiKV selected one documentation section, normalized formatting, retained bounded excerpts, and shortened it at a paragraph or sentence boundary for retrieval. Verify version-sensitive details at the source.