The AsyncGeneratorFunction constructor creates a new async generator function object. In JavaScript, every async generator function is actually an AsyncGeneratorFunction object.

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

const AsyncGeneratorFunction = (async function* () {}).constructor;


new AsyncGeneratorFunction(functionBody)
new AsyncGeneratorFunction(arg0, functionBody)
new AsyncGeneratorFunction(arg0, arg1, functionBody)
new AsyncGeneratorFunction(arg0, arg1, /* … ,*/ argN, functionBody)

AsyncGeneratorFunction(arg0, functionBody)
AsyncGeneratorFunction(arg0, arg1, functionBody)
AsyncGeneratorFunction(arg0, arg1, /* … ,*/ argN, functionBody)

Note: AsyncGeneratorFunction() can be called with or without new. Both create a new AsyncGeneratorFunction instance.


argN Optional

Names to be used by the function as formal argument names. Each must be a string that corresponds to a valid JavaScript parameter (any of plain identifier, rest parameter, or destructured parameter, optionally with a default), or a list of such strings separated with commas.

As the parameters are parsed in the same way as function declarations, whitespace and comments are accepted. For example: "x", "theValue = 42", "[a, b] /* numbers */" — or "x, theValue = 42, [a, b] /* numbers */". ("x, theValue = 42", "[a, b]" is also correct, though very confusing to read.)


A String containing the JavaScript statements comprising the function definition.


Async generator function objects created with the AsyncGeneratorFunction constructor are parsed when the function is created. This is less efficient than declaring a generator function with an async 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, except the last, 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: Async generator functions created with the AsyncGeneratorFunction 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 AsyncGeneratorFunction constructor was called.

This is different from using eval with code for an async generator function expression.

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


Using the constructor

The following example uses the AsyncGeneratorFunction constructor to create an async generator function.

const AsyncGeneratorFunction = (async function* () {}).constructor;
const createAsyncGenerator = new AsyncGeneratorFunction('a', 'yield a * 2');
const asyncGen = createAsyncGenerator(10); => console.log(res.value)); // 20


ECMAScript Language Specification
# sec-asyncgeneratorfunction-objects

Browser compatibility

BCD tables only load in the browser

See also