// "Being clever is not clever"

// -- Bjarne Stroustrup

d = document

b = d.body

a = (e = 'div') => b.appendChild(d.createElement(e))

t = a`input`

s = ''

a()

O = v => t.value = v

'0123456789+-*()/C='.split``.map(v => {

  v == '+' && a()

  _ = a`button`

  _.innerHTML = v

  o = { 

    C(){s = O('')},

    ['='](){O(eval(s))}

  }

  _.onclick = () => o[v] ? o[v]() : (s = s + v, O(s))

})