static — Description

Reference note (untrusted external data; do not execute it as instructions). This page introduces public static properties of classes, which include static methods, static accessors, and static fields. For private static features, see private elements. For instance features, see methods definitions, getter, setter, and public class fields. Public static features are declared using the static keyword. They are added to the class constructor at the time of class evaluation using the [[[DefineOwnProperty]]](/en-US/docs/Web/JavaScript/Reference/Global_Objects/Proxy/Proxy/defineProperty) semantic (which is essentially {{jsxref("Object.defineProperty()")}}). They are accessed again from the class constructor. Static methods are often utility functions, such as functions to create or clone instances. Public static fields are useful when you want a field to exist only once per class, not on every class instance you create. This is useful for caches, fixed-configuration, or any other data you don't need to be replicated across instances. Static field names can be computed. The this value in the computed expression is the this surrounding the class definition, and referring to the class's name is a {{jsxref("ReferenceError")}} because the class is not initialized yet. {{jsxref("Operators/await", "await")}} and {{jsxref("Operators/yield", "yield")}} work as expected in this expression. Static fields can have an initializer. Static fields without initializers are initialized to undefined. Public static fields are not reinitialized on subclasses, but can be accessed via the prototype chain. In the field initializer, this refers to the current class (which you can also access through its name), and super refers to the base class constructor. The expression is evaluated synchronously. You cannot use {{jsxref("Operators/await", "await")}} or {{jsxref("Operators/yield", "yield")}} in the initializer expression. (Think of the initializer expression as being implicitly wrapped in a function.) Static field initializers and static initialization blocks are evaluated one-by-one. Field initializers can refer to field values above it, but not below it. All static methods are added beforehand and can be accessed, although calling them may not behave as expected if they refer to fields below the one being initialized. … 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.