How to get the public key that signed the transaction in JavaScript

publicKeyTx.js

/* Example of how to obtain the public key that
 * signed the Tx
 */

/* Requires needed. You have to install the following
 * packages
 * npm install ethereumjs-util ethereumjs-tx
 */
const ethereumTx = require('ethereumjs-tx').Transaction;
const eth_util = require('ethereumjs-util')

// Signed Tx
let signedTx = "" // Add the signed Tx (NOT the Tx hash)

let rawTx = new ethereumTx(signedTx).toJSON(true)
console.log("The raw Tx is:\n", rawTx)

let buffTx = {
	nonce: eth_util.toBuffer(rawTx.nonce),
	gasPrice: eth_util.toBuffer(rawTx.gasPrice),
	gasLimit: eth_util.toBuffer(rawTx.gasLimit),
	to: eth_util.toBuffer(rawTx.to),
	value: eth_util.toBuffer(rawTx.value),
	data: eth_util.toBuffer(rawTx.data)
}

let rlpencoded = eth_util.rlphash(Object.values(buffTx))
let pkey = eth_util.ecrecover(rlpencoded, rawTx.v,
	eth_util.toBuffer(rawTx.r),
	eth_util.toBuffer(rawTx.s))

console.log("\nThe public key is: 0x" + pkey.toString('hex'))