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.
Note: generator function
created with the GeneratorFunction
constructor do not create closures to their creation contexts; they are always created in the global scope.
When running them, they will only be able to access their own local variables and global ones, not the ones from the scope in which the GeneratorFunction
constructor was called.
This is different from using eval
with code for a generator function expression.
Invoking the GeneratorFunction
constructor as a function (without using the new
operator) has the same effect as invoking it as a constructor.
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 |
---|
ECMAScript (ECMA-262) The definition of 'GeneratorFunction' in that specification. |
Browser compatibility
Desktop | Mobile | Server | |||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|
GeneratorFunction | Chrome Full support 39 | Edge Full support 13 | Firefox Full support 26 | IE No support No | Opera Full support 26 | Safari Full support 10 | WebView Android Full support 39 | Chrome Android Full support 39 | Firefox Android Full support 26 | Opera Android Full support 26 | Safari iOS Full support 10 | Samsung Internet Android Full support 4.0 | nodejs Full support Yes |
Legend
- Full support
- Full support
- No support
- No support