javascript – Invalid checksum when generating BIP-39 Mnemonic

There is a few problem in your code, in the hendecadsFromBits function, you need to use the numeric value of bit and in the generateMnemonic function, when you call hendecadsFromBits, you need to pass the result to Array.from()

Here is how you could fix your code:

export const generateMnemonic = async () => {
    const ent = window.crypto.getRandomValues(new Uint8Array(16));
    const entBits = toBinString(ent);
    const entHash = Array.from(new Uint8Array(
        await window.crypto.subtle.digest("SHA-256", ent)
    ));
    const entHashBits = toBinString(entHash)
    const checksum = entHashBits.slice(0, 4);
    const entCS = entBits + checksum;
    const chunks = Array.from(hendecadsFromBits(entCS));
    const words = [];

    for (let i = 0; i < chunks.length; i++) {
        words.push(wordlist[chunks[i]]);
    }
    return words.join(' ');
};

const toBinString = (bytes) => bytes.reduce((str, byte) => str + byte.toString(2).padStart(8, '0'), '')

function* hendecadsFromBits(bits) {
    let i = 0;
    let val = 0;
    for (const bit of bits) {
        if (i == 11) {
            yield val;
            i = val = 0;
        }
        val |= parseInt(bit, 10) << i++;
    }
    if (i > 0) yield val;
}