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## Is
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### Instructions
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Add new function properties to the `is` object to check value types. Each function should take one argument, and return a `boolean`.
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- `is.num`: value is a `number`.
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- `is.nan`: value is `NaN`.
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- `is.str`: value is a `string`.
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- `is.bool`: value is a `boolean`.
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- `is.undef`: value is `undefined`.
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- `is.def`: value is defined.
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- `is.arr`: value is an `array`.
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- `is.obj`: value is a simple object or `null` objects.
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- `is.fun`: value is a function.
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- `is.truthy`: value is truthy.
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- `is.falsy`: value is falsy.
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### Examples
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```js
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console.log(is.num(5))
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// output: true
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console.log(is.num('ciao'))
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// output: false
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```
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### Notions
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- [Primitives and operators](https://nan-academy.github.io/js-training/examples/primitive-and-operators.js)
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- [typeof](https://devdocs.io/javascript/operators/typeof)
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- [Truthy](https://developer.mozilla.org/en-US/docs/Glossary/Truthy)
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- [Falsy](https://developer.mozilla.org/en-US/docs/Glossary/Falsy)
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### Code provided
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> The provided code will be added to your solution, and does not need to be submitted.
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```js
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const is = {}
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```
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