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 Function(arg1, functionBody)
new Function(arg1, arg2, functionBody)
new Function(arg1, ... , 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 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.) 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 Language Specification # sec-generatorfunction-objects |
Browser compatibility
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