CFP - Docs - flattenOnce

flattenOnce

```
(anArray: array) => array
```

Flatten an array one level deep.

flattenOnce(['a', ['b', ['c']]]) // is ['a', 'b', ['c']]
flattenOnce(['a', ['b', ['c']]]) // is ['a', 'b', ['c']]

Try It

flattenOnce(['a', ['b', ['c']]]) // is ['a', 'b', ['c']]
flattenOnce(['a', ['b', ['c']]]) // is ['a', 'b', ['c']]

Sometimes we have nested arrays and only want to flatten one level deep. Below, a doctor is examining the medical history of relatives and wants to limit her search to the patient's cousins. Let's flatten the tree one level to do this.

Try It

const secondCousins = ['amy', 'kim']
const cousins = ['matt', 'jason']
const siblings = ['phil', 'mary', 'sarah']
const extendedFamily = [...siblings, [...cousins, [...secondCousins]]]

const isString = element => typeof element === 'string'
const siblingsAndCousins = flattenOnce(extendedFamily).filter(isString)
console.log(siblingsAndCousins)
// is [
//   phil,
//   mary,
//   sarah,
//   matt,
//   jason,
// ]
const secondCousins = ['amy', 'kim']
const cousins = ['matt', 'jason']
const siblings = ['phil', 'mary', 'sarah']

type FamilyTree = (string | FamilyTree)[]
const extendedFamily: FamilyTree = [
  ...siblings,
  [...cousins, [...secondCousins]],
]

const isString = (node: string | FamilyTree) => typeof node === 'string'
const siblingsAndCousins = flattenOnce(extendedFamily).filter(isString)
console.log(siblingsAndCousins)
// is [
//   phil,
//   mary,
//   sarah,
//   matt,
//   jason,
// ]

Try It

const secondCousins = ['amy', 'kim']
const cousins = ['matt', 'jason']
const siblings = ['phil', 'mary', 'sarah']
const extendedFamily = [
  ...siblings,
  [...cousins, [...secondCousins]],
]

const isString = element =>
  typeof element === 'string'
const siblingsAndCousins = flattenOnce(
  extendedFamily
).filter(isString)
console.log(siblingsAndCousins)
// is [
//   phil,
//   mary,
//   sarah,
//   matt,
//   jason,
// ]
const secondCousins = ['amy', 'kim']
const cousins = ['matt', 'jason']
const siblings = ['phil', 'mary', 'sarah']

type FamilyTree = (string | FamilyTree)[]
const extendedFamily: FamilyTree = [
  ...siblings,
  [...cousins, [...secondCousins]],
]

const isString = (node: string | FamilyTree) =>
  typeof node === 'string'
const siblingsAndCousins = flattenOnce(
  extendedFamily
).filter(isString)
console.log(siblingsAndCousins)
// is [
//   phil,
//   mary,
//   sarah,
//   matt,
//   jason,
// ]