js rc4解密

function rc4Decrypt(key, data) {
  let s = [];
  let j = 0;
  let out = [];

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

  for (let i = 0; i < 256; i++) {
    j = (j + s[i] + key.charCodeAt(i % key.length)) % 256;
    [s[i], s[j]] = [s[j], s[i]];
  }

  let i = 0;
  j = 0;

  for (let k = 0; k < data.length; k++) {
    i = (i + 1) % 256;
    j = (j + s[i]) % 256;
    [s[i], s[j]] = [s[j], s[i]];
    let t = (s[i] + s[j]) % 256;
    out.push(data[k] ^ s[t]);
  }

  return String.fromCharCode.apply(null, out);
}