function to calculate sha256 from string without using crypto or any other library in javascript

index.tsx
function sha256(str) {
  // Convert string to utf-8 byte array
  const utf8 = unescape(encodeURIComponent(str));
  const bytes = [...utf8].map(c => c.charCodeAt(0));

  // Initial Hash Values
  const h = [
    0x6a09e667,
    0xbb67ae85,
    0x3c6ef372,
    0xa54ff53a,
    0x510e527f,
    0x9b05688c,
    0x1f83d9ab,
    0x5be0cd19
  ];

  // Constants
  const k = [
    0x428a2f98,
    0x71374491,
    0xb5c0fbcf,
    0xe9b5dba5,
    0x3956c25b,
    0x59f111f1,
    0x923f82a4,
    0xab1c5ed5,
    0xd807aa98,
    0x12835b01,
    0x243185be,
    0x550c7dc3,
    0x72be5d74,
    0x80deb1fe,
    0x9bdc06a7,
    0xc19bf174,
    0xe49b69c1,
    0xefbe4786,
    0x0fc19dc6,
    0x240ca1cc,
    0x2de92c6f,
    0x4a7484aa,
    0x5cb0a9dc,
    0x76f988da,
    0x983e5152,
    0xa831c66d,
    0xb00327c8,
    0xbf597fc7,
    0xc6e00bf3,
    0xd5a79147,
    0x06ca6351,
    0x14292967,
    0x27b70a85,
    0x2e1b2138,
    0x4d2c6dfc,
    0x53380d13,
    0x650a7354,
    0x766a0abb,
    0x81c2c92e,
    0x92722c85,
    0xa2bfe8a1,
    0xa81a664b,
    0xc24b8b70,
    0xc76c51a3,
    0xd192e819,
    0xd6990624,
    0xf40e3585,
    0x106aa070,
    0x19a4c116,
    0x1e376c08,
    0x2748774c,
    0x34b0bcb5,
    0x391c0cb3,
    0x4ed8aa4a,
    0x5b9cca4f,
    0x682e6ff3,
    0x748f82ee,
    0x78a5636f,
    0x84c87814,
    0x8cc70208,
    0x90befffa,
    0xa4506ceb,
    0xbef9a3f7,
    0xc67178f2
  ];

  // Pre-processing
  bytes.push(0x80); // Add bit "1" to end of message
  while ((bytes.length * 8) % 512 !== 448) {
    bytes.push(0x00); // Add zeros until length is divisible by 512
  }
  const msgLenBits = str.length * 8;
  const lenBytes = [
    (msgLenBits >>> 56) & 0xff,
    (msgLenBits >>> 48) & 0xff,
    (msgLenBits >>> 40) & 0xff,
    (msgLenBits >>> 32) & 0xff,
    (msgLenBits >>> 24) & 0xff,
    (msgLenBits >>> 16) & 0xff,
    (msgLenBits >>> 8) & 0xff,
    msgLenBits & 0xff
  ];
  bytes.push(...lenBytes);

  // Chunkify
  const chunks = [];
  for (let i = 0; i < bytes.length; i += 64) {
    chunks.push(bytes.slice(i, i + 64));
  }

  // Process each chunk
  for (let i = 0; i < chunks.length; i++) {
    const w = new Array(64).fill(0);
    for (let j = 0; j < 16; j++) {
      w[j] =
        (chunks[i][j * 4] << 24) |
        (chunks[i][j * 4 + 1] << 16) |
        (chunks[i][j * 4 + 2] << 8) |
        chunks[i][j * 4 + 3];
    }

    for (let j = 16; j < 64; j++) {
      const s0 =
        (w[j - 15] >>> 7) ^
        (w[j - 15] >>> 18) ^
        (w[j - 15] >>> 3);
      const s1 =
        (w[j - 2] >>> 17) ^
        (w[j - 2] >>> 19) ^
        (w[j - 2] >>> 10);
      w[j] = (w[j - 16] + s0 + w[j - 7] + s1) & 0xffffffff;
    }

    let [a, b, c, d, e, f, g, h] = h;
    for (let j = 0; j < 64; j++) {
      const S1 = (e >>> 6) ^ (e >>> 11) ^ (e >>> 25);
      const ch = (e & f) ^ (~e & g);
      const temp1 = (h + S1 + ch + k[j] + w[j]) & 0xffffffff;
      const S0 = (a >>> 2) ^ (a >>> 13) ^ (a >>> 22);
      const maj = (a & b) ^ (a & c) ^ (b & c);
      const temp2 = (S0 + maj) & 0xffffffff;

      h = g;
      g = f;
      f = e;
      e = (d + temp1) & 0xffffffff;
      d = c;
      c = b;
      b = a;
      a = (temp1 + temp2) & 0xffffffff;
    }

    h = (h + h0) & 0xffffffff;
    g = (g + g0) & 0xffffffff;
    f = (f + f0) & 0xffffffff;
    e = (e + e0) & 0xffffffff;
    d = (d + d0) & 0xffffffff;
    c = (c + c0) & 0xffffffff;
    b = (b + b0) & 0xffffffff;
    a = (a + a0) & 0xffffffff;
  }

  // Concatenate hash values
  const hash = new Uint32Array([a, b, c, d, e, f, g, h]).reduce(
    (acc, val) => {
      let str = val.toString(16);
      str = "0".repeat(8 - str.length) + str;
      return `${acc}${str}`;
    },
    ""
  );

  return hash;
}
3704 chars
174 lines

index.tsx
const hash = sha256("Hello, world!");
console.log(hash); // Outputs "b94d27b9934d3e08a52e52d7da7dabfac484efe37a5380ee9088f7ace2efcde9"
135 chars
3 lines