flatten(array) js code example

Example 1: javascript array flatten

// flat(depth), 
// depth is optional: how deep a nested array structure 
//		should be flattened.
//		default value of depth is 1 

const arr1 = [1, 2, [3, 4]];
arr1.flat(); 
// [1, 2, 3, 4]

const arr2 = [1, 2, [3, 4, [5, 6]]];
arr2.flat();
// [1, 2, 3, 4, [5, 6]]

const arr3 = [1, 2, [3, 4, [5, 6]]];
arr3.flat(2);
// [1, 2, 3, 4, 5, 6]

const arr4 = [1, 2, [3, 4, [5, 6, [7, 8, [9, 10]]]]];
arr4.flat(Infinity);
// [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]

Example 2: flatten an array in javascript

function flatten(arr) {
  const result = []

  arr.forEach((i) => {
    if (Array.isArray(i)) {
      result.push(...flatten(i))
    } else {
      result.push(i)
    }
  })
  
  return result
}

// Usage
const nested = [1, 2, 3, [4, 5, [6, 7], 8, 9]]

flatten(nested) // [1, 2, 3, 4, 5, 6, 7, 8, 9]