PKI.js is a pure JavaScript library implementing the formats that are used in PKI applications (signing, encryption, certificate requests, OCSP and TSP requests/responses). It is built on WebCrypto (Web Cryptography API) and requires no plug-ins.
@peculiar/x509 is an easy to use TypeScript/Javascript library based on @peculiar/asn1-schema that makes generating X.509 Certificates and Certificate Requests as well as validating certificate chains easy