RC4, what did I do wrong?

Question

JavaScript

I found an implementation of rc4 for JS, by analogy I wrote for C ++. In js I encrypt 1234 with key 1, I get the result. I copy the result from the browser tab, paste it into the C ++ algorithm, try to decrypt it, but always an error of one character. I can not find where I made a mistake and why the error. Could it be a coding issue?

function rc4(key, str) {
  var s = [], j = 0, x, res = '';

  for (var i = 0; i < 256; i++) {
    s[i] = i;
  }
  for (i = 0; i < 256; i++) {
    j = (j + s[i] + key.charCodeAt(i % key.length)) % 256;
    x = s[i];
    s[i] = s[j];
    s[j] = x;
  }
  i = 0;
  j = 0;
  for (var y = 0; y < str.length; y++) {
    i = (i + 1) % 256;
    j = (j + s[i]) % 256;
    x = s[i];
    s[i] = s[j];
    s[j] = x;
    res += String.fromCharCode(str.charCodeAt(y) ^ s[(s[i] + s[j]) % 256]);
  }
  return res;
}

var key = "1";
var str = "1234";

Encryption result: Q(ñY

int main()
{
  string key = "1";
  string text = "Q(ñY";
  string code = string();

  code = my_rc4((char*)key.c_str(), key.size(), (char*)text.c_str(), text.size());

  cout << "text: " << text << "\n";
  cout << "code: " << code << "\n";

  system("pause");
  return 0;
}
string my_rc4(char* key, size_t key_size, char* text, size_t text_size)
{
  int s[256];
  int j = 0;
  int x = int();

  string res = string();

  for (size_t i = 0; i < 256; ++i)
  {
    s[i] = i;
  }

  for (size_t i = 0; i < 256; ++i)
  {
    j = (j + s[i] + (int)key[i % key_size]) % 256;

    x = s[i];

    s[i] = s[j];

    s[j] = x;
  }

  int i = 0;
  j = 0;

  for (int y = 0; y < text_size; ++y)
  {
    i = (i + 1) % 256;
    j = (j + s[i]

Answer 1

Your code is incomplete.