Flattens nested array to given depth.
[:package:](https://www.npmjs.com/package/@extra-array/flat)
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> Alternatives: [flat], [flatMap].

> This is part of package [extra-array].

[extra-array]: https://www.npmjs.com/package/extra-array

<br>

```javascript
array.flat(x, [n], [fm], [ft]);
// x:  a nested array
// n:  maximum depth (-1 => all)
// fm: map function (v, i, x)
// ft: test function (v, i, x)
```

```javascript
const array = require("extra-array");

var x = [[1, 2], [3, [4, [5]]]];
array.flat(x);
// [ 1, 2, 3, 4, 5 ]

array.flat(x, 1);
// [ 1, 2, 3, [ 4, [ 5 ] ] ]

array.flat(x, 2);
// [ 1, 2, 3, 4, [ 5 ] ]
```

<br>
<br>


## References

- [Array.prototype.flat: MDN web docs](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/flat)
- [_.flatten: lodash](https://lodash.com/docs/#flatten)
- [_.flattenDeep: lodash](https://lodash.com/docs/4.17.15#flattenDeep)
- [_.flattenDepth: lodash](https://lodash.com/docs/4.17.15#flattenDepth)
- [Array.flatten: sugarjs](https://sugarjs.com/docs/#/Array/flatten)

[flat]: https://github.com/nodef/extra-array/wiki/flat
[flatMap]: https://github.com/nodef/extra-array/wiki/flatMap