###### tags `javascript`,`2021`

# SHA256 not depend on package

var sha256 = function sha256(ascii) {
    function rightRotate(value, amount) {
        return (value >>> amount) | (value << (32 - amount));
    };

    var mathPow = Math.pow;
    var maxWord = mathPow(2, 32);
    var lengthProperty = 'length'
    var i, j; // Used as a counter across the whole file
    var result = ''

    var words = [];
    var asciiBitLength = ascii[lengthProperty] * 8;

    var hash = sha256.h = sha256.h || [];

    var k = sha256.k = sha256.k || [];
    var primeCounter = k[lengthProperty];


    var isComposite = {};
    for (var candidate = 2; primeCounter < 64; candidate++) {
        if (!isComposite[candidate]) {
            for (i = 0; i < 313; i += candidate) {
                isComposite[i] = candidate;
            }
            hash[primeCounter] = (mathPow(candidate, .5) * maxWord) | 0;
            k[primeCounter++] = (mathPow(candidate, 1 / 3) * maxWord) | 0;
        }
    }

    ascii += '\x80' // Append Ƈ' bit (plus zero padding)
    while (ascii[lengthProperty] % 64 - 56) ascii += '\x00' // More zero padding
    for (i = 0; i < ascii[lengthProperty]; i++) {
        j = ascii.charCodeAt(i);
        if (j >> 8) return; // ASCII check: only accept characters in range 0-255
        words[i >> 2] |= j << ((3 - i) % 4) * 8;
    }
    words[words[lengthProperty]] = ((asciiBitLength / maxWord) | 0);
    words[words[lengthProperty]] = (asciiBitLength)

    // process each chunk
    for (j = 0; j < words[lengthProperty];) {
        var w = words.slice(j, j += 16);
        var oldHash = hash;

        hash = hash.slice(0, 8);

        for (i = 0; i < 64; i++) {
            var i2 = i + j;
            var w15 = w[i - 15], w2 = w[i - 2];

            var a = hash[0], e = hash[4];
            var temp1 = hash[7]
                + (rightRotate(e, 6) ^ rightRotate(e, 11) ^ rightRotate(e, 25)) // S1
                + ((e & hash[5]) ^ ((~e) & hash[6])) // ch
                + k[i]

                + (w[i] = (i < 16) ? w[i] : (
                    w[i - 16]
                    + (rightRotate(w15, 7) ^ rightRotate(w15, 18) ^ (w15 >>> 3)) // s0
                    + w[i - 7]
                    + (rightRotate(w2, 17) ^ rightRotate(w2, 19) ^ (w2 >>> 10)) // s1
                ) | 0
                );

            var temp2 = (rightRotate(a, 2) ^ rightRotate(a, 13) ^ rightRotate(a, 22)) // S0
                + ((a & hash[1]) ^ (a & hash[2]) ^ (hash[1] & hash[2])); // maj

            hash = [(temp1 + temp2) | 0].concat(hash);
            hash[4] = (hash[4] + temp1) | 0;
        }

        for (i = 0; i < 8; i++) {
            hash[i] = (hash[i] + oldHash[i]) | 0;
        }
    }

    for (i = 0; i < 8; i++) {
        for (j = 3; j + 1; j--) {
            var b = (hash[i] >> (j * 8)) & 255;
            result += ((b < 16) ? 0 : '') + b.toString(16);
        }
    }
    return result;
};

Reference: [stackoverflow](https://stackoverflow.com/questions/59777670/how-can-i-hash-a-string-with-sha256-in-js)
Tool: [線上加解密](https://emn178.github.io/online-tools/sha256.html)