Convert a byte array to a word array and back in CryptoJS-compatible fashion

CryptoJS_byteArrayWordArrayConversions.js

function byteArrayToWordArray(ba) {
	var wa = [],
		i;
	for (i = 0; i < ba.length; i++) {
		wa[(i / 4) | 0] |= ba[i] << (24 - 8 * i);
	}

	return CryptoJS.lib.WordArray.create(wa, ba.length);
}

function wordToByteArray(word, length) {
	var ba = [],
		i,
		xFF = 0xFF;
	if (length > 0)
		ba.push(word >>> 24);
	if (length > 1)
		ba.push((word >>> 16) & xFF);
	if (length > 2)
		ba.push((word >>> 8) & xFF);
	if (length > 3)
		ba.push(word & xFF);

	return ba;
}

function wordArrayToByteArray(wordArray, length) {
	if (wordArray.hasOwnProperty("sigBytes") && wordArray.hasOwnProperty("words")) {
		length = wordArray.sigBytes;
		wordArray = wordArray.words;
	}

	var result = [],
		bytes,
		i = 0;
	while (length > 0) {
		bytes = wordToByteArray(wordArray[i], Math.min(4, length));
		length -= bytes.length;
		result.push(bytes);
		i++;
	}
	return [].concat.apply([], result);
}

I wrote an unit test for this. This implementation works only for converting Uint8Array to CryptoJS.lib.WordArray and back.
It fails for converting CryptoJS.lib.WordArray to Uint8Array and back, the reverse conversion returns different values. That's really bad.

code:
` // ORIGINAL IMPLEMENTATION

static ba2wa(ba) {
var wa = [],
i;
for (i = 0; i < ba.length; i++) {
wa[(i / 4) | 0] |= ba[i] << (24 - 8 * i);
}

return CryptoJS.lib.WordArray.create(wa, ba.length);

}

private static w2ba(word, length) {
var ba = [],
i,
xFF = 0xFF;
if (length > 0)
ba.push(word >>> 24);
if (length > 1)
ba.push((word >>> 16) & xFF);
if (length > 2)
ba.push((word >>> 8) & xFF);
if (length > 3)
ba.push(word & xFF);

return ba;

}

static wa2ba(wordArray, length) {
if (wordArray.hasOwnProperty("sigBytes") && wordArray.hasOwnProperty("words")) {
length = wordArray.sigBytes;
wordArray = wordArray.words;
}

var result = [],
  bytes,
  i = 0;
while (length > 0) {
  bytes = this.w2ba(wordArray[i], Math.min(4, length));
  length -= bytes.length;
  result.push(bytes);
  i++;
}
return [].concat.apply([], result);

}
`

test:
`
it('should convert a large CryptoJS.lib.WordArray to a Uint8Array and back to the same CryptoJS.lib.WordArray',
() => {
// Arrange
const input = CryptoJS.lib.WordArray.random(10);
console.log(JSON.stringify(input.words));

    // Act
    const result1 = WordArrayExtensions.wa2ba(input, null);
    const result2 = WordArrayExtensions.ba2wa(result1);

    // Assert
    expect(result1).toBeDefined();
    expect(result2).toBeDefined();
    expect(result2.words).toEqual(input.words);
  });

`

thank a lot <3

Combined and rewrote the words-to-bytes-function to be a bit faster. Just in case someone needs it.

function cryptArrToByteArr(wordArray) {
        var bytes = new Uint8Array(wordArray.sigBytes);

        var fullwords = wordArray.sigBytes >>> 2; //equal div 4
        var lastbytes = wordArray.sigBytes % 4;

        var word, offs;
        for (var i = 0; i < fullwords; i++) {
                word = wordArray.words[i];
                offs = i<<2;
                bytes[offs] = word >>> 24;
                bytes[offs+1] = (word >>> 16) & 0xFF;
                bytes[offs+2] = (word >>> 8) & 0xFF;
                bytes[offs+3] = word & 0xFF;
        }
        if (lastbytes > 0) {
                word = wordArray.words[fullwords];
                offs = fullwords<<2;
                bytes[offs] = word >>> 24;
                if (length > 1) bytes[offs+1] = (word >>> 16) & 0xFF;
                if (length > 2) bytes[offs+2] = (word >>> 8) & 0xFF;
        }
        return bytes;
}

The above code has errors too, although I definitely prefer its intended efficiency:

     if (lastbytes > 0) {
             word = wordArray.words[fullwords];
             offs = fullwords<<2;
             bytes[offs] = word >>> 24;
             if (lastbytes > 1) bytes[offs+1] = (word >>> 16) & 0xFF;
             if (lastbytes > 2) bytes[offs+2] = (word >>> 8) & 0xFF;
     }

In case anyone comes here looking for a solution, here is what I ended up using:

/** Returns a crypto-JS compatible Word Array, based on the byte array provided */
  static toWordArray(bytes) {
    var words = [];
    for (var j = 0; j < bytes.length; j++) {
      words[(j>>>2)] |= bytes[j] << (24 - (8 * (j%4)));
    }
    return CryptoJS.lib.WordArray.create(words, bytes.length);
  }

  /** Returns a byte array, based on the crypto-JS compatible word array provided */
  static fromWordArray(wordArray) {
    var bytes = new Uint8Array(wordArray.sigBytes);
    for (var j=0; j<wordArray.sigBytes; j++) {
      bytes[j] = (wordArray.words[(j>>>2)] >>> (24 - (8 * (j%4)))) & 0xFF
    }
    return bytes;
  }