Sample code for 30+ languages & platforms
Node.js

Duplicate openssl dgst -md5 -sign myKey.pem something.txt | openssl enc -base64 -A

See more RSA Examples

Demonstrates how to duplicate the creation of an RSA signature produced by this OpenSSL command:
openssl dgst -md5 -sign myKey.pem something.txt | openssl enc -base64 -A

Chilkat Node.js Downloads

Node.js
NODEJS_PRELUDE

function chilkatExample() {

    var success = false;

    // This example assumes the Chilkat API to have been previously unlocked.
    // See Global Unlock Sample for sample code.

    var pkey = new chilkat.PrivateKey();

    // Load the private key from an RSA PEM file:
    success = pkey.LoadPemFile("myKey.pem");

    var rsa = new chilkat.Rsa();

    // Import the private key into the RSA component:
    success = rsa.UsePrivateKey(pkey);
    if (success == false) {
        console.log(rsa.LastErrorText);
        return;
    }

    // OpenSSL uses BigEndian byte ordering:
    rsa.LittleEndian = false;

    // The resulting signature will be a Base64 string:
    rsa.EncodingMode = "base64";

    // For simplicity, we're not loading
    // the data to be signed from a file.  We are instead simply
    // using a literal string value.  
    var strData = "This is the text to be signed.";

    // Hash the input using MD5, and then sign the hash:
    // Other valid hash algorithm choices are "md2" and "sha-1".
    var base64Sig = rsa.SignStringENC(strData,"md5");

    console.log(base64Sig);

    console.log("Success!");

}

chilkatExample();