How to use Forge library and pfx file to sign plain text?

Question

    const pkcs12 = forge.pkcs12;
    const pkcs12Der = arrayBufferToString(pfxData)
    const p12Asn1 = forge.asn1.fromDer(pkcs12Der);
    const p12 = pkcs12.pkcs12FromAsn1(p12Asn1, password);
    const certBags = p12.getBags({ bagType: forge.pki.oids.certBag });
    const cert = certBags\[forge.pki.oids.certBag\]\[0\].cert;
    const keyBags = p12.getBags({ bagType: forge.pki.oids.pkcs8ShroudedKeyBag });
    const key = keyBags\[forge.pki.oids.pkcs8ShroudedKeyBag\]\[0\].key;

    const signer = forge.pki.createSigner({
       md: forge.md.sha256.create(),
       rsaOptions: {
       key: forge.pki.privateKeyToPem(key),
     },
    });
    
    signer.certificates = \[cert\];
    
    signer.update(text);
    const signature = signer.sign();
    
    console.log(signature);

'pfxData' is the binary data of the pfx file. 'password' is password of the pfx file. 'text' is the text to be signed. Which method should be used for signing?