Flatten a nested array in Javascript

flat.js

//
// [email protected]
//
// For this solution, when a project has lodash, I would suggest to use `flattenDeep` @ https://lodash.com/docs/4.17.4#flattenDeep
// But ofcourse, a manual util function is easily written:

const nestedArray = [1, [2, 3], [4, 5, [6, 7]], 8]

function flattenArray (nestedArray) {
  let flatArray = []
  
  function flatten (array, newArray) {
    for (let i = 0; i < array.length; i++) {
      if (!Array.isArray(array[i])) {
        newArray.push(array[i])
      } else {
        flatten(array[i], newArray)
      }
    }
  }

  flatten(nestedArray, flatArray)
  return flatArray
}

const flattenedArray = flattenArray(nestedArray)

console.log(flattenedArray)