Parsing X509 Certificate using pkijs

index.js

const atob = require('atob');
const asn1js = require('asn1js');
const fs = require('fs');
const pkijs = require('pkijs');
const pvutils = require('pvutils')

const Certificate = pkijs.Certificate

let certificateBuffer = new ArrayBuffer(0);

function init () {
    let pemFile = fs.readFileSync('f.pem','utf8');
    certificateBuffer = convertPemToBinary(pemFile);
    console.log(certificateBuffer);
    printCertificate(certificateBuffer);
}

function convertPemToBinary(pem) {
    var lines = pem.split('\n');
    var encoded = '';
    for(var i = 0;i < lines.length;i++){
      if (lines[i].trim().length > 0 &&
          lines[i].indexOf('-BEGIN RSA PRIVATE KEY-') < 0 && 
          lines[i].indexOf('-BEGIN RSA PUBLIC KEY-') < 0 &&
          lines[i].indexOf('-BEGIN PUBLIC KEY-') < 0 &&
          lines[i].indexOf('-BEGIN CERTIFICATE-') < 0 &&
          lines[i].indexOf('-BEGIN PRIVATE KEY-') < 0 &&
          lines[i].indexOf('-END PRIVATE KEY-') < 0 &&
          lines[i].indexOf('-END CERTIFICATE-') < 0 &&
          lines[i].indexOf('-END PUBLIC KEY-') < 0 &&
          lines[i].indexOf('-END RSA PRIVATE KEY-') < 0 &&
          lines[i].indexOf('-END RSA PUBLIC KEY-') < 0) {
        encoded += lines[i].trim();
      }
    }
    return base64StringToArrayBuffer(encoded);
  }

  function base64StringToArrayBuffer(b64str) {
    let byteStr = atob(b64str);

    let bytes = new Uint8Array(byteStr.length);
    for (let i = 0; i < byteStr.length; i++) {
      bytes[i] = byteStr.charCodeAt(i);
    }
    return bytes.buffer;
  }
  
function printCertificate (certificateBuffer) {
    let asn1 = asn1js.fromBER(certificateBuffer);
    if(asn1.offset === (-1)) {
        console.log("Can not parse binary data");
    } 

    const certificate = new Certificate({ schema: asn1.result });
    console.log(certificate);
    console.log('Certificate Serial Number');
    console.log(pvutils.bufferToHexCodes(certificate.serialNumber.valueBlock.valueHex));
    console.log('Certificate Issuance');
    console.log(certificate.notBefore.value.toString());
    console.log('Certificate Expiry');
    console.log(certificate.notAfter.value.toString());
    console.log(certificate.issuer);
}

init();

Run node index.js and observe the results