Flatten a multidimensional array

readme.md

Flatten an array

With recursion

The recursive approach is concise but there is the concern of overflowing the call stack. That can be solved with a generator.

With iteration

An iterative approach is also good to know

We loop through the array with a while loop and we take out an item from the array one at a time to check to see if that item is an array. If the item is not an array, we put it into the res array. If it is an array, we use a spread operator ... to get all the items out of it and put them back to the array. using Array.prototype.some

flatten.js

function flatten(value){
  //do this immutably without modifying the initial arr
  value.reduce((acc, cur) => acc.concat(Array.isArray(curr) ? flatten(curr): curr), [])
}



//iteration
function flatten(value){
  const res = []
  const copy = value.slice()
  
  while(copy.length){
    const item = copy.shift()
    if(Array.isArray(item)){
      copy.unshift(...item)
    }else{
      res.push(item)
    }
  }
  
  return res
}


//written more concisely
function flatten(value){
  while(value.some(Array.isArray)){
    value = [].concat(...value)
  }
  return value
}