var x = [
 '1',
 12,
 [1, 2, { a: 'z' }],
 { a: 'zzz' }
]


function ArrayToString(x) {
  var result = '[ '
  for(var i = 0; i < x.length; i++) {
    if(x[i].constructor === Object) {
      result = result + ObjectToString(x[i])
    } else if(x[i].constructor === Array) {
      result = result + ArrayToString(x[i])
    } else if(x[i].constructor === Function) {
      result = result + x[i].toString()
    } else {
      result = result + x[i]
    }
    if(x.length != i + 1) result = result + ', '
  }
  result = result + ' ]'
  return result;
}


function ObjectToString(x) {
  var result = '{ '
  for(var i in x) {
    if(x[i].constructor === Object) {
      result = result + i + ': ' + ObjectToString(x[i])
    } else if(x[i].constructor === Array) {
      result = result + i + ': ' + ArrayToString(x[i])
    } else if(x[i].constructor === Function) {
      result = result + i + ': ' + x[i].toString()
    } else {
      result = result + i + ': ' + x[i]
    }
    result = result + ', '
  }
  result = result + ' }'
  return result;
}

ArrayToString(x)