Decrypting cipher with aes-256-cbc with iv using nodejs crypto module - node.js

Question

Am porting a python AES-256 Encrypt/Decrypt method to its nodejs equivalent.But am having an error on the nodejs side when decrypting the cipher.
crypto.js:267
this._handle.initiv(cipher, toBuf(key), toBuf(iv));
^
Error: Invalid IV length
at new Decipheriv (crypto.js:267:16)
at Object.createDecipheriv (crypto.js:627:10)
at CryptoUtils.AESDecrypt
The python Encrypt/Decrypt Method:
def AESEncrypt(key, plaintext):
plaintext = AESPad(plaintext)
iv = os.urandom(AES.block_size)
cipher = AES.new(key, AES.MODE_CBC, iv)
return iv + cipher.encrypt(plaintext)
def AESDecrypt(key, ciphertext):
iv = ciphertext[:AES.block_size];
cipher = AES.new(key, AES.MODE_CBC, iv);
plaintext = cipher.decrypt(ciphertext[AES.block_size:]);
return AESUnpad(plaintext);
My nodejs attempt to convert it:
AESEncrypt(key, plaintext) {
const _plaintext = this.AESPad(plaintext)
const iv = crypto.randomBytes(AES_BLOCK_SIZE) //synchronous
const cipher = crypto
.createCipheriv("aes-256-cbc", key, iv)
.update(_plaintext)
return iv + cipher
}
AESDecrypt(key, ciphertext) {
const iv = ciphertext.slice(0, 16)
console.log("iv", iv)
const plaintext = crypto
.createDecipheriv("aes-256-cbc", key, iv)
.update(ciphertext.substring(16))
return this.AESUnpad(plaintext)
What am i doing wrong? My nodejs version is v8.11.2 and Python 2.7.15rc1