Converts a multiArray into a flatArray - Code sample

flattenArray.js

function getFlatArray(multiArray){
  let flatArray = [];
  for(var item of multiArray) {
    if(item instanceof Array){
      flatArray.push(...getFlatArray(item))
    }else {
      flatArray.push(item);
    }
  }
  return flatArray;
}

const multiArray = [[1,2,[3]],4];
console.log('The result is: ', getFlatArray(multiArray));