Promise.prototype

The Promise.prototype property represents the prototype for the Promise constructor.

Description

Promise instances inherit from Promise.prototype. You can use the constructor's prototype object to add properties or methods to all Promise instances.

Properties

Promise.prototype.constructor

Returns the function that created an instance's prototype. This is the Promise function by default.

Methods

Promise.prototype.catch(onRejected)

Appends a rejection handler callback to the promise, and returns a new promise resolving to the return value of the callback if it is called, or to its original fulfillment value if the promise is instead fulfilled.

Promise.prototype.then(onFulfilled, onRejected)

Appends fulfillment and rejection handlers to the promise, and returns a new promise resolving to the return value of the called handler, or to its original settled value if the promise was not handled (i.e. if the relevant handler onFulfilled or onRejected is not a function).

Specifications

Specification	Status	Comment
ECMAScript 2015 (6th Edition, ECMA-262) The definition of 'Promise.prototype' in that specification.	Standard	Initial definition.
ECMAScript 2017 Draft (ECMA-262) The definition of 'Promise.prototype' in that specification.	Draft

Browser compatibility

See also

• Promise