//var ctext = rc4("我是明文","我是密码");
//var text = rc4(ctext, "我是密码");
function rc4(data, key) {
  var seq = Array(256); //int
  var das = Array(data.length); //code of data
  for (var i = 0; i < 256; i++) {
    seq[i] = i;
    var j = (j + seq[i] + key.charCodeAt(i % key.length)) % 256;
    var temp = seq[i];
    seq[i] = seq[j];
    seq[j] = temp;
  }
  for (var i = 0; i < data.length; i++) {
    das[i] = data.charCodeAt(i)
  }
  for (var x = 0; x < das.length; x++) {
    var i = (i + 1) % 256;
    var j = (j + seq[i]) % 256;
    var temp = seq[i];
    seq[i] = seq[j];
    seq[j] = temp;
    var k = (seq[i] + (seq[j] % 256)) % 256;
    das[x] = String.fromCharCode(das[x] ^ seq[k]);
  }
  return das.join('');
}