function fn(){console.log('fn print')}
function fn1(){console.log('fn1 print')}
function fnthis(){console.log(this);}

console.log(fn.call == Function.call)
console.log(fn.call.call == Function.call)
console.log(Function.call.call == Function.call)

fn.call(fn1)
fn.call.call(fn1)
Function.call(fn1)
Function.call.call(fn1)

fn.call(fnthis)
fn.call.call(fnthis)
Function.call(fnthis)
Function.call.call(fnthis)

function md5(string) {
  function RotateLeft(lValue, iShiftBits) {
    return ((lValue << iShiftBits) | (lValue >>> (32 - iShiftBits))) & 0xFFFFFFFF;
  }

  // https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number/MAX_SAFE_INTEGER
  function unsignAdd(lX, lY) {
    return ((lX & 0xFFFFFFFF) + (lY & 0xFFFFFFFF) ) & 0xFFFFFFFF;
  }

  // (a,b,c,d) = (d, ((a+f(b,c,d) + data + Ki)<<< s)+b, b, c)
  function f(a, b, c, d, x, s, ac, Fn) {
    return unsignAdd(RotateLeft(unsignAdd(a, unsignAdd(unsignAdd(Fn(b, c, d), x), ac)), s), b);
  }

  function ConvertToWordArray(string) {
    let lWordCount;
    let lMessageLength = string.length;
    // https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number/MAX_SAFE_INTEGER
    let lNumberOfWords_temp1 = lMessageLength + 8;
    let lNumberOfWords_temp2 = (lNumberOfWords_temp1 - (lNumberOfWords_temp1 % 64)) / 64;
    let lNumberOfWords = (lNumberOfWords_temp2 + 1) * 16;
    let lWordArray = Array(lNumberOfWords - 1);
    let lBytePosition = 0;
    let lByteCount = 0;
    while (lByteCount < lMessageLength) {
      lWordCount = (lByteCount - (lByteCount % 4)) / 4;
      lBytePosition = (lByteCount % 4) * 8;
      lWordArray[lWordCount] = (lWordArray[lWordCount] | (string.charCodeAt(lByteCount) << lBytePosition));
      lByteCount++;
    }
    lWordCount = (lByteCount - (lByteCount % 4)) / 4;
    lBytePosition = (lByteCount % 4) * 8;
    lWordArray[lWordCount] = lWordArray[lWordCount] | (0x80 << lBytePosition);
    lWordArray[lNumberOfWords - 2] = lMessageLength << 3;
    lWordArray[lNumberOfWords - 1] = lMessageLength >>> 29;
    return lWordArray;
  };
  function WordToHex(v) {
    let WordToHexValue = "";
    for (let i = 0; i < 4; i++) {
      WordToHexValue += `0${((v >>> (i * 8)) & 0xFF).toString(16)}`.substr(-2);
    }
    return WordToHexValue;
  };
  function Utf8Encode(string) {
    let utftext = "";
    for (let n = 0; n < string.length; n++) {
      let c = string.charCodeAt(n);
      if (c < 128) {
        utftext += String.fromCharCode(c);
      } else if ((c > 127) && (c < 2048)) {
        utftext += String.fromCharCode((c >> 6) | 192);
        utftext += String.fromCharCode((c & 63) | 128);
      } else {
        utftext += String.fromCharCode((c >> 12) | 224);
        utftext += String.fromCharCode(((c >> 6) & 63) | 128);
        utftext += String.fromCharCode((c & 63) | 128);
      }
    }
    return utftext;
  };
  let x = ConvertToWordArray(Utf8Encode(string));

  let funcs = [
    (x,y,z) => ((x & y) | ((~x) & z) ),
    (x,y,z) => ((x & z) | (y & (~z))),
    (x,y,z) => (x ^ y ^ z),
    (x,y,z) => (y ^ (x | (~z)))
  ];
  // K = abs(sin(i+1))*(2^32) int part
  // https://softwareengineering.stackexchange.com/questions/89694/md5-implementation-notes
  const K = [ 0xD76AA478 ,0xE8C7B756 ,0x242070DB ,0xC1BDCEEE ,0xF57C0FAF ,0x4787C62A ,0xA8304613 ,0xFD469501 ,0x698098D8 ,0x8B44F7AF ,0xFFFF5BB1 ,0x895CD7BE ,0x6B901122 ,0xFD987193 ,0xA679438E ,0x49B40821 ,0xF61E2562 ,0xC040B340 ,0x265E5A51 ,0xE9B6C7AA ,0xD62F105D ,0x02441453 ,0xD8A1E681 ,0xE7D3FBC8 ,0x21E1CDE6 ,0xC33707D6 ,0xF4D50D87 ,0x455A14ED ,0xA9E3E905 ,0xFCEFA3F8 ,0x676F02D9 ,0x8D2A4C8A ,0xFFFA3942 ,0x8771F681 ,0x6D9D6122 ,0xFDE5380C ,0xA4BEEA44 ,0x4BDECFA9 ,0xF6BB4B60 ,0xBEBFBC70 ,0x289B7EC6 ,0xEAA127FA ,0xD4EF3085 ,0x04881D05 ,0xD9D4D039 ,0xE6DB99E5 ,0x1FA27CF8 ,0xC4AC5665 ,0xF4292244 ,0x432AFF97 ,0xAB9423A7 ,0xFC93A039 ,0x655B59C3 ,0x8F0CCC92 ,0xFFEFF47D ,0x85845DD1 ,0x6FA87E4F ,0xFE2CE6E0 ,0xA3014314 ,0x4E0811A1 ,0xF7537E82 ,0xBD3AF235 ,0x2AD7D2BB ,0xEB86D391 ] ;

  const S = [[7,12,17,22],[5,9,14,20],[4,11,16,23],[6,10,15,21]];

  const offset = [[1,0],[5,1],[3,5],[7,0]];

  // 01234567 89abcdef fedcba98 76543210
  let abcd = [0x67452301,0xEFCDAB89,0x98BADCFE,0x10325476];

  // http://www.faqs.org/rfcs/rfc1321.html
  for (let idx = 0; idx < x.length; idx += 16) {
    const ABCD = [...abcd];
    for(let i = 0;i < 4;i ++){
      for(let j = 0;j < 4;j ++){
        for(let k = 0;k < 4;k ++){
          abcd = [abcd[3],f(...abcd, x[idx + ((offset[i][0]*(j*4+k) + offset[i][1] ) %16)], S[i][k], K[(i*4+j)*4+k], funcs[i]),abcd[1],abcd[2]];
        }
      }
    }
    abcd = ABCD.map((item,idx)=> unsignAdd(item,abcd[idx]));
  }
  return abcd.map(item=>WordToHex(item)).join('').toLowerCase();
}

console.log(md5(""))
console.log(md5("demo"))