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30-seconds-of-code/snippets/functions.md
Angelos Chalaris 37d70bf58f Combined functions and functionsIn
Makes more sense that way, following the example of flatten.
2018-01-12 13:37:33 +02:00

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### functions
Returns an array of function property names from own (and optionally inherited) enumerable properties of an object.
Use `Object.keys(obj)` to iterate over the object's own properties.
If `inherited` is `true`, use `Object.get.PrototypeOf(obj)` to also get the object's inherited properties.
Use `Array.filter()` to keep only those properties that are functions.
Omit the second argument, `inherited`, to not include inherited properties by default.
```js
const functions = (obj, inherited = false) =>
(inherited ? [...Object.keys(obj), ...Object.keys(Object.getPrototypeOf(obj))] : Object.keys(obj)).filter(key => typeof obj[key] === 'function');
```
```js
function Foo() {
this.a = () => 1;
this.b = () => 2;
}
Foo.prototype.c = () => 3;
functions(new Foo()); // ['a', 'b']
functions(new Foo(), true); // ['a', 'b', 'c']
```