23 lines
678 B
Markdown
23 lines
678 B
Markdown
### functionsIn
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Returns an array of function property names from own and inherited enumerable properties of object.
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Use `Object.keys(obj)` and `Object.get.PrototypeOf(obj)` to iterate over the object's own and inherited properties, `Array.filter()` to keep only those that are functions.
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Use the spread operator (`...`) to combine all returned property names into one array.
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```js
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const functionsIn = obj =>
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[...Object.keys(obj), ...Object.keys(Object.getPrototypeOf(obj))].filter(
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key => typeof obj[key] === 'function'
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);
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```
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```js
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function Foo() {
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this.a = () => 1;
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this.b = () => 2;
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}
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Foo.prototype.c = () => 3;
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functionsIn(new Foo()); // ['a', 'b', 'c']
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```
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