A few quick notes about some of the less obvious aspects of interacting with Maxonrow in JavaScript.


The use of console.log can substantially impact performance. For this reason, you may wish to reduce the log level to not show info and warnings.
change Log Level
// The default is "info"; other options
// "debug", "info", "warn", "error", "off"

Why can’t I just use numbers?

The first problem many encounter when dealing with Maxonrow is the concept of numbers. Most common currencies are broken down with very little granularity. For example, there are only 100 cents in a single dollar. However, there are 1018 cin in a single mxw.

JavaScript uses IEEE 754 double-precision binary floating point numbers to represent numeric values. As a result, there are holes in the integer set after 9,007,199,254,740,991; which is problematic for Maxonrow because that is only around 0.009 mxw (in cin).

To demonstrate how this may be an issue in your code, consider:

> (Number.MAX_SAFE_INTEGER + 4 - 5) == (Number.MAX_SAFE_INTEGER - 1)

To remedy this, all numbers (which can be large) are stored and manipulated as Big Numbers.

The functions parseMxw( mxwString ) and formatMxw( cin ) can be used to convert between string representations, which are displayed to or entered by the user and Big Number representations which can have mathematical operations handled safely.


A Promise in JavaScript is an object which simplifies many aspects of dealing with asynchronous functions.

It allows a pending result to be treated in many ways as if it has already been resolved.

The most useful operations you will need are:

Promise . all ( promises )
Returns a new promise that resolves once all the promises have resolved.
prototype . then ( onResolve, onReject )

Returns another Promise, which once the Promise was resolved, the onResolve function will be executed and if an error occurs, onReject will be called.

If onResolve returns a Promise, it will be inserted into the chain of the returned promise. If onResolve throws an Error, the returned Promise will reject.

get account details in JavaScript
var mxw = require('mxw-sdk-js');

var targetAddress = "mxw1x7tp9tt7mu0jm6qdmljgntvzzp53lrtndr7h8x";
var provider = mxw.getDefaultProvider();

// Promises that we are interested in
var balancePromise = provider.getBalance(targetAddress);
var transactionCountPromise = provider.getTransactionCount(targetAddress);

var allPromises = Promise.all([

var sendPromise = allPromises.then(function(results) {
     // This function is ONLY called once ALL promises are fulfilled

     var balance = results[0];
     var transactionCount = results[1];

     return {

sendPromise.then(function(account) {
    // This will be called once the details is available
    console.log("Address:", targetAddress);
    console.log("Balance:", account.balance.toString());
    console.log("Nonce:", account.transactionCount().toString());


I fully welcome anyone to contribute to the project, and appreciate all the help I can get. That said, if you have ideas for a PR, please discuss them as an issue on GitHub first.

A few notes on contributing.

  • An important feature of mxw-sdk-js is that it is small, which means uncommon features or large features need a great deal of discussion.
  • Dependencies; part A) in line with the above, “keep things small”, adding a dependency is a big deal, as they often bring many other packages with them. A great deal of effort has been used to tune the build process and dependency list to keep things tight
  • Dependencies; part B) adding additional third party libraries, adds a huge attack vector fun malicious code or unexpected consequences, so adding a dependency is certainly something that needs to be very convincingly argued.
  • Dependencies; part C) part B applies to dev dependencies too. A devDependency can inject or otherwise do strange things and increases the attack vector for bugs and malicious code
  • Changing filenames or breaking backwards compatibility is a no-go for minor version changes
  • Major version changes do not happen often. We place @TODO in the source code for things that will be updated at the next version change.
  • Please use the GitHub issue system to make requests, or discuss changes you would like to make.
  • Testing is a must. It should generally take you longer to write test cases than it does the actual code.
  • All test cases must pass on all platforms supported.


A lot of people store a lot of value in Ethereum and the code that runs it. As such, security is important.

The GitHub and NPM Package

The keys used to sign code on GitHub are well protected, but anyones computer can be compromised.

All services involved have two-factor authentication set up, but please keep in mind that bleeding-edge technology should probably not be used in production environments.

Keep in mind, however, that at the end of the day, if NPM were hacked, anything in the system could be replaced.

By using a version that is perhaps a few weeks old, providing there are no advisories otherwise, there has been adequate time for any compromise to have been broadcast.

Also, one of the test cases verifies the deterministic build on Continuous Integration (CI). Never install a version which has failed the CI tests.

Long story short, be careful.

In the event of any significant issue, it will be posted on the file, have an issue posted, with ALL CAPS in the title and will be broadcast on the official channels.

Memory Hard Brute-Force Encrpyting

A topic that often comes up is the poor performance of decrypting Wallet.

While it may not be immediately obvious, this is intentional for security purposes.

If it takes the legitimate user, who knows the password 5 seconds or so to unlock their account, that means that an attacker must spend 5 seconds per password attempt, so to guess a million passwords, requires 5 million seconds. Client software can streamline the process by using Secure Enclaves or other secure local places to store the decrypted wallet to improve the customer experience past the first decryption.

Responsible Disclosure

If you find a critical bug or security issue, please contact so that we can address it before you make it public. You will receive credit for the discovery after it is fixed and announced. :)