@extra-array/find-index/README.md

Finds index of leftmost value passing a test.

Finds index of leftmost value passing a test. [:running:] [:vhs:] [:package:] [:moon:] [:ledger:]
> Alternatives: [findIndex], [findIndices].<br>
> Similar: [find], [findIndex].<br>
> This is part of package [extra-array].

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

```javascript
array.findIndex(x, fn);
// x:  an array
// fn: test function (v, i, x)
// --> index of value, -1 if not found
```

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

var x = [1, 2, 3, 4, 5];
array.findIndex(x, v => v % 2 == 0);
// 1        ^

array.findIndex(x, v => v % 2 == 1);
// 0     ^
```

### references

- [Data.List.findIndex: Haskell](http://hackage.haskell.org/package/base-4.12.0.0/docs/Data-List.html#v:findIndex)
- [List-Extra.findIndex: elm](hhttps://package.elm-lang.org/packages/elm-community/list-extra/7.1.0/List-Extra#findIndex)
- [_.findIndex: lodash](https://lodash.com/docs/4.17.15#findIndex)
- [Array.findIndex: sugarjs](https://sugarjs.com/docs/#/Array/findIndex)

[:running:]: https://npm.runkit.com/@extra-array/find-index
[:package:]: https://www.npmjs.com/package/@extra-array/find-index
[:moon:]: https://www.npmjs.com/package/@extra-array/find-index.min
[:ledger:]: https://unpkg.com/@extra-array/find-index/
[findIndex]: https://github.com/nodef/extra-array/wiki/findIndex
[findIndices]: https://github.com/nodef/extra-array/wiki/findIndices
[find]: https://github.com/nodef/extra-array/wiki/find
[:vhs:]: https://asciinema.org/a/332048