Flatten A Jagged Multi Dimensional Array

I need help flattening an array like this: [1,2,[2,3],[5,[6,1],4],7] I want it to be something like [1,2,2,3,5,6,1,4,7]. I have searched something like this, and found [].concat

Solution 1:

My recommendation would be to take a dependency on lodash and use the flattenDeep function.

_.flattenDeep([1,2,[2,3],[5,[6,1],4],7])
// [ 1, 2, 2, 3, 5, 6, 1, 4, 7 ]

If you want to write your own function, you might want to peek at the lodash implementation.

In pseudo-code, here's a recursive approach:

result= []
function flatten(array)
  foreach element inarray
    if element isarray
      flatten(element)
    else
      result.append(element)

EDIT

Here's a "by-hand" approach, though I'd definitely recommend relying on the better-tested lodash implementation.

functionflatten(arr, result) {
  if (result === undefined) {
    result = [];
  }

  for (var i = 0; i < arr.length; i++) {
    if (Array.isArray(arr[i])) {
      flatten(arr[i], result);
    } else {
      result.push(arr[i]);
    }
  }

  return result;
}

console.log(flatten([1, 2, [2, 3], [5, [6, 1], 4], 7]));

// Output:// [ 1, 2, 2, 3, 5, 6, 1, 4, 7 ]

Solution 2:

You can wrap the concat.apply thing in a loop to handle deeply nested arrays:

while (a.some(Array.isArray))
    a = [].concat.apply([], a)

or in the ES6 syntax:

while (a.some(Array.isArray)) 
    a = [].concat(...a);