Before these Mnemonic functionality in tronweb was not available in packge npm version 4.4.0. It was recently released. Usage examples:
const TronWeb = require('tronweb');
console.log(TronWeb.fromMnemonic('patch left empty genuine rain normal syrup yellow consider moon stock denial',"m/44'/195'/0'/0/3"));
exit:
{
privateKey: '781C49346BC8F7BCE6FF54FCD6D1A486E5F01238207124FC57DBFBDD91F325B6',
publicKey: '0421274E7431BFEE7428A42E71DB43D97773813CC50CE9FCA6D82CC72AED36618A1A3BF81B56967D888586F8240DE2078F798CB653AB1C7B681D2C2E82EA2B5A14',
address: {
base58: 'TFaC1WRiabPe8PU7NEFtPuPuLoHmtUSEkK',
hex: '413D765BFA4E0D353931737D80393C6AD78F459EB7'
}
}
Visit: https://developers.tron.network/reference/frommnemonic