aws-cognito-rsa

gistfile1.js

// Library
var jwkToPem = require('jwk-to-pem');

// Paste your JWK here
var key='{"alg":"RS256","e":"","kid":"","kty":"RSA","n":"","use":"sig"}';

// Parse the key
key = JSON.parse(key);

// Convert to RSA Public Key (.pem)
var jwk = {kty: key.kty, n: key.n, e: key.e};

// Print to console
console.log(jwk);

Last few lines should be

// Convert to RSA Public Key (.pem)
var jwk = {kty: key.kty, n: key.n, e: key.e},
pem = jwkToPem(jwk);

// Print to console
console.log(pem);