Flatten

09 February 2018

Every other interview I’m asked to implement a flatten function that receives an array and returns a flattened version of it. They may request different ways to handle edge cases, but my usual answer is in the lines of…

function flatten (collection = []) {
  let result = []

  collection.forEach(item => {
    if (Array.isArray(item))
      result = result.concat(flatten(item))
    else
      result.push(item)
  })

  return result
}

Are there better ways to do it? Definitely, but at an early interview stage this is usually good enough.

I’m still glad this comes up more often than implementing mergeSort.