Example of using CosmJS with `protobufjs` to encode a custom proto message

script.js

// Every chain has at least two API endpoints: 26657 (the Tendermint one, roughly
// speaking, lower level, deals with bytes, exposes info about blocks, consensus,
// validators, etc.) and 1317 (the Cosmos one, higher level, your chain's API).
// Since every transaction broadcasted to a chain should be signed (and you don't
// want to do the signing manually), it makes sense to use a signing library.
// For JS/TS it's CosmJS.

// With CosmJS you create a wallet from a mnemonic, create a client from a wallet,
// and use client.signAndBroadcast method to, well, sign and broadcast transaction
// (an array of messages from an address). The client uses 26657 endpoint under the
// hood and needs to know how to encode your messages. For that a client has a registry.
// Let's consider an example.

// We use protobufjs to create a type with fields that mirrors what we have in our proto,
// pass the type to the registry and broadcast our message.

import { coins } from "@cosmjs/launchpad";
import { SigningStargateClient } from "@cosmjs/stargate";
import { Registry, DirectSecp256k1HdWallet } from "@cosmjs/proto-signing";
import { Type, Field } from "protobufjs";

const MsgCreatePost = new Type("MsgCreatePost")
  .add(new Field("creator", 1, "string"))
  .add(new Field("title", 2, "string"))
  .add(new Field("body", 3, "string"));

const typeUrl = "/foo.foo.MsgCreatePost";
const registry = new Registry([[typeUrl, MsgCreatePost]]);

const api = "http://localhost:26657";
const mnemonic =
  "slight recycle much magnet crumble spatial jar rotate drill soccer exhaust wrap scale horse catalog camera talent account rice business trial unit kitten noble";
const wallet = await DirectSecp256k1HdWallet.fromMnemonic(mnemonic);
const stargate = SigningStargateClient;
const client = await stargate.connectWithWallet(api, wallet, { registry });
const fromAddress = await wallet.address;

const msg = {
  typeUrl,
  value: {
    title: "foo1",
    body: "bar1",
    creator: fromAddress,
  },
};

const fee = {
  amount: coins(0, "token"),
  gas: "200000",
};

await client.signAndBroadcast(fromAddress, [msg], fee)

tx.proto

syntax = "proto3";
package foo.foo;

message MsgCreatePost {
  string creator = 1;
  string title = 2; 
  string body = 3; 
}