A utility function to flatten a deeply nested array

flattenDeeplyNestedArray.js

export default function flattenDeeplyNestedArray(array) {

  return array.reduce((flattenedArray, value) => {

    if (Array.isArray(value)) {

      // If our value is an array itself, flatten again before concating
      return flattenedArray.concat(flattenDeeplyNestedArray(value))

    } else {

      // Otherwise simply concat it to the reducing array
      return flattenedArray.concat(value)

    }
  }, [])

}