How to create actions in JavaScript environment


A long time ago, I surveyed GraphQL mutations’ usage and researched a way to replace that.

Even then, I tried the way, named lib9c-wasm, WASM library to use lib9c logics in a JavaScript environment. There was no time to develop it more but we decided to make a web reference implementation with the lib9c-wasm library in this quarter. See How to play web9c for it.

This article won’t explain the web9c. It’ll explain how to create actions in a JavaScript environment with the lib9c-wasm.


Project setup

At first, create a new directory. Like a demo

mkdir lib9c-wasm-demo
cd lib9c-wasm-demo

Then, install the necessary dependencies.

yarn add -D typescript ts-node @types/node
yarn add @planetarium/tx @planetarium/lib9c-wasm @planetarium/account @planetarium/bencodex

Write a code to create a transaction (bridge exchange)

The below code just creates a transfer_asset3 transaction and shows it on your console. You can replace the <RAW_PRIVATE_KEY> with your own private key, the nonce: 0n with your account’s nonce, the memo: "ETHEREUM_ADDRESS" with your Ethereum address, and majorUnit: "10" with the NCG amount you want to exchange.

import { RawPrivateKey } from "@planetarium/account";
import {
} from "@planetarium/tx";
import { Address, Currency, transfer_asset3 } from "@planetarium/lib9c-wasm";
import { decode, encode } from "@planetarium/bencodex";

const NCG = new Currency({
    ticker: "NCG",
    decimalPlaces: 2,
    minters: [new Address("0x47d082a115c63e7b58b1532d20e631538eafadde")],

// Replacable with another implementations.
const account = RawPrivateKey.fromHex("<RAW_PRIVATE_KEY>");  // Test or your own private key.

async function main() {
    const signer = await account.getAddress();
    // Send 10 NCG.
    const action = transfer_asset3({
        sender: new Address(signer.toHex()),
        recipient: new Address("0x9093dd96c4bb6b44a9e0a522e2de49641f146223"),  // Example address, bridge address.
        amount: {
            currency: NCG,
            sign: 1,
            majorUnit: "10",
            minorUnit: "0",
        memo: "ETHEREUM_ADDRESS",

    const signedTx = await signTx({
        nonce: 10n,
        publicKey: (await account.getPublicKey()).toBytes("uncompressed"),
        signer: signer.toBytes(),
        timestamp: new Date(,
        updatedAddresses: new Set(),
        genesisHash: Buffer.from("4582250dq0da33b06779a8475d283d5dd210c683b9b999d74d03fac4f58fa6bce", "hex"),
        customActions: [decode(action)],
        gasLimit: null,
        maxGasPrice: null
    }, account);
    const serializedSignedTx = encode(encodeSignedTx(signedTx));

main().then(_ => console.log("finished.")).catch(console.error);

If you replace the fields and stage it with GraphQL API, the transaction will be included in mainnet blocks. Such an example is web9c. If you wonder another example or have questions, please leave them as comments or as issues in the lib9c-wasm repository.

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