arr2.js

const test1 = [
    [1, 2, 3, '4'],
    [false, [1, 2], '6']
  ],
  test2 = [
    [
      [1, 78],
      [false, 'true'],
      [45, 'foo']
    ],
    [3, 5]
  ]

arr = test2

function ea4(arr) {
  var addem = []
  run(arr)

  function run(arr) {
    arr.forEach(element => {
      console.log('ELEMENT = ' + element)
      console.log(element)
      if (Array.isArray(element)) {
        console.log('returning')
        return run(element);
      }
      if (Number.isInteger(element)) {
        console.log(element)
        console.log('this ' + element + ' is ' + Number.isInteger(element))
        addem.push(element)
        console.log('add array now = ')
        console.log(addem)
      } else {
        console.log(element + ' will not be added ')
        return
      }
    });
  }
  console.log(addem)
  result = addem.reduce(function (a, b) {
    return a + b;
  })
  console.log('total = ' + result)
}

ea4(arr);