GeneratorFunction

The GeneratorFunction constructor creates a new generator function object. In JavaScript every generator function is actually a GeneratorFunction object.

Note that GeneratorFunction is not a global object. It could be obtained by evaluating the following code.

Object.getPrototypeOf(function*(){}).constructor

Syntax

new GeneratorFunction ([arg1[, arg2[, ...argN]],] functionBody)

Parameters

arg1, arg2, ... argN

Names to be used by the function as formal argument names. Each must be a string that corresponds to a valid JavaScript identifier or a list of such strings separated with a comma; for example "x", "theValue", or "a,b".

functionBody

A string containing the JavaScript statements comprising the function definition.

Description

generator function objects created with the GeneratorFunction constructor are parsed when the function is created. This is less efficient than declaring a generator function with a function* expression and calling it within your code, because such functions are parsed with the rest of the code.

All arguments passed to the function are treated as the names of the identifiers of the parameters in the function to be created, in the order in which they are passed.

Invoking the GeneratorFunction constructor as a function (without using the new operator) has the same effect as invoking it as a constructor.

Properties

GeneratorFunction.length

The GeneratorFunction constructor's length property whose value is 1.

GeneratorFunction.prototype

Allows the addition of properties to all generator function objects.

GeneratorFunction prototype object

Properties

GeneratorFunction instances

GeneratorFunction instances inherit methods and properties from GeneratorFunction.prototype. As with all constructors, you can change the constructor's prototype object to make changes to all GeneratorFunction instances.

Examples

Creating a generator function from a GeneratorFunction constructor

var GeneratorFunction = Object.getPrototypeOf(function*(){}).constructor
var g = new GeneratorFunction('a', 'yield a * 2');
var iterator = g(10);
console.log(iterator.next().value); // 20

Specifications

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

Browser compatibility

See also

• function* function
• function* expression
• Function
• function statement
• function expression
• Functions and function scope