const arr1 = [
  {
    'a': 1, 
    'fn1': () => {}
  }, 
  'b',
  1,
  true,
  {
    'fn2': () => {}
  }
];

const jstringify = value => JSON.parse(JSON.stringify(value))

const deepCopy = array => {  
  return arr1.reduce((acc, item) => {
    if (String(item) === '[object Object]') {
      const savedFn = {}
      if (Object.keys(item).forEach(key => typeof item[key] === 'function')) {
        savedFn[key] = item[key]
      }
      acc.push({ ...item, ...savedFn })
    } else {
      acc.push(item)
    }
    return acc;
  }, [])
}

const arr = [[1], 2, 3]

const shallow = arr.map(x => x)

arr[0].push(5)

console.log(shallow) // [[1, 5], 2, 3]