FunctionDescriptor.js

A function that returns an object with information describing the function. This works with user and non-user defined functions.

Usage:

function test(name) {
  return "hello " + name;
}

//parameter MUST be a function or otherwise it will throw a TypeError
let info = describeFunction(test);

info.name; // => "test"
info.params; // => ["name"];
info.type; // => "function";



// This below will throw a TypeError because the parameter is not a "function"
describeFunction(null);

return value

describeFunction() returns an object with these properties:

Property	Value	Description
.name	String	Returns the name of the function.
.type	String	Returns a string with the type of defined function with one of these values: "function", "class", "arrow", "getter", "setter".
.params	String[]	Returns an Array with the names of the parameters. This does not return the parameter value! However, this can return an empty array as it only collects named parameters in the function code.
.isNative	Boolean	Returns a boolean indicating it has only native code in the function.
.isBound	Boolean	Returns a boolean indicating that the function is a bind function that was created from .bind().
.isBindable	Boolean	Returns a boolean indicating that this function can be used with .bind().
.isAsync	Boolean	Returns a boolean indicating that this function is an AsyncFunction.
.isGenerator	Boolean	Returns a boolean indication thatthis function is a GeneratorFunction

Example:

This example below checks if the function is an AsyncGeneratorFunciton Object

function isAsyncGenerator(fn) {
  let info = describeFunction(fn);
  return info.isAsync && info.isGenerator;
}

async function* myAsync() {}


isAsyncGenerator(myAsync); // expected output: true