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20.0.0-beta3.0.3 • Public • Published

⚠️ Important! We recently released a major breaking rewrite for vktjs. Be sure to lock your dependencies. ⚠️

If you are looking for the the previous version of vktjs you can find it here.


Javascript API for integration with EOSIO-based blockchains using EOSIO RPC API.

Documentation can be found here


NodeJS Dependency

npm install vktjs@beta or yarn add vktjs@beta

Browser Distribution

Clone this repository locally then run npm run build-web or yarn build-web. The browser distribution will be located in dist-web and can be directly copied into your project repository. The dist-web folder contains minified bundles ready for production, along with source mapped versions of the library for debugging. For full browser usage examples, see the documentation.


ES Modules

Importing using ES6 module syntax in the browser is supported if you have a transpiler, such as Babel.

import { Api, JsonRpc, RpcError } from 'vktjs';

import JsSignatureProvider from 'eosjs/dist/eosjs-jssig'; // development only


Importing using commonJS syntax is supported by NodeJS out of the box.

const { Api, JsonRpc, RpcError } = require('vktjs');
const JsSignatureProvider = require('vktjs/dist/eosjs-jssig');  // development only
const fetch = require('node-fetch');                            // node only; not needed in browsers
const { TextEncoder, TextDecoder } = require('util');           // node only; native TextEncoder/Decoder
const { TextEncoder, TextDecoder } = require('text-encoding');  // React Native, IE11, and Edge Browsers only

Basic Usage

Signature Provider

The Signature Provider holds private keys and is responsible for signing transactions.

Using the JsSignatureProvider in the browser is not secure and should only be used for development purposes. Use a secure vault outside of the context of the webpage to ensure security when signing transactions in production

const defaultPrivateKey = "5JtUScZK2XEp3g9gh7F8bwtPTRAkASmNrrftmx4AxDKD5K4zDnr"; // useraaaaaaaa
const signatureProvider = new JsSignatureProvider([defaultPrivateKey]);


Open a connection to JSON-RPC, include fetch when on NodeJS.

const rpc = new JsonRpc('', { fetch });


Include textDecoder and textEncoder when using in browser.

const api = new Api({ rpc, signatureProvider, textDecoder: new TextDecoder(), textEncoder: new TextEncoder() });

Sending a transaction

transact() is used to sign and push transactions onto the blockchain with an optional configuration object parameter. This parameter can override the default value of broadcast: true, and can be used to fill TAPOS fields given blocksBehind and expireSeconds. Given no configuration options, transactions are expected to be unpacked with TAPOS fields (expiration, ref_block_num, ref_block_prefix) and will automatically be broadcast onto the chain.

(async () => {
  const result = await api.transact({
    actions: [{
      account: 'eosio.token',
      name: 'transfer',
      authorization: [{
        actor: 'useraaaaaaaa',
        permission: 'active',
      data: {
        from: 'useraaaaaaaa',
        to: 'useraaaaaaab',
        quantity: '0.0001 SYS',
        memo: '',
  }, {
    blocksBehind: 3,
    expireSeconds: 30,

Error handling

use RpcError for handling RPC Errors

try {
  const result = await api.transact({
} catch (e) {
  console.log('\nCaught exception: ' + e);
  if (e instanceof RpcError)
    console.log(JSON.stringify(e.json, null, 2));

Running Tests

Automated Unit Test Suite

npm run test or yarn test

Web Integration Test Suite

Run npm run build-web to build the browser distrubution then open src/tests/web.html in the browser of your choice. The file should run through 6 tests, relaying the results onto the webpage with a 2 second delay after each test. The final 2 tests should relay the exceptions being thrown onto the webpage for an invalid transaction and invalid rpc call.




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