https://thai-mecc.go.th/share/js/lib/asmcrypto/pbkdf2-core.js

1function pbkdf2core(hmac, salt, length, count) {
2    const result = new Uint8Array(length);
3    const blocks = Math.ceil(length / hmac.HMAC_SIZE);
4    for (let i = 1; i <= blocks; ++i) {
5        const j = (i - 1) * hmac.HMAC_SIZE;
6        const l = (i < blocks ? 0 : length % hmac.HMAC_SIZE) || hmac.HMAC_SIZE;
7        hmac.reset().process(salt);
8        hmac.hash.asm.pbkdf2_generate_block(hmac.hash.pos, hmac.hash.len, i, count, 0);
9        result.set(hmac.hash.heap.subarray(0, l), j);
10    }
11    return result;
12}