node aes cryptor

aes.js

const crypto = require('crypto');
const cryptor = {
  encrypt(cryptkey, iv, cleardata) {
    cryptkey = crypto.createHash('sha256').update(cryptkey).digest();
    const encipher = crypto.createCipheriv('aes-256-cbc', cryptkey, iv);
    let encryptdata = encipher.update(cleardata, 'utf8', 'binary');
    encryptdata += encipher.final('binary');
    return new Buffer(encryptdata, 'binary').toString('base64');
  },
  decrypt(cryptkey, iv, encryptdata) {
    cryptkey = crypto.createHash('sha256').update(cryptkey).digest();
    encryptdata = new Buffer(encryptdata, 'base64').toString('binary');
    const decipher = crypto.createDecipheriv('aes-256-cbc', cryptkey, iv);
    let decoded = decipher.update(encryptdata, 'binary', 'utf8');
    decoded += decipher.final('utf8');
    return decoded;
  }
}

@kukukukikii How do you calculate the iv in this case?