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ethereumweb3jstrufflebignumber.js

Calling web3.utils.BN.add gives error: Cannot create property 'negative' on number

At truffle test, I am trying to add two Big Numbers together using the following code:

myBignumber = new web3.utils.BN(1);
myBignumber.add(2)

But it caused this error:

Cannot create property 'negative' on number 2

Versions:

  • Truffle 5.0
  • Web3 1.0
Solution

  • The BN used at Web3 has some open issues (ref)

    Suggested Alternative:

    Try using another BigNumber library that has a working addition function (like this).

    To use the library install it:

    npm install bignumber.js

    Now at your truffle test:

        var BigNumber = require("bignumber.js");

    ...
    // Instead of the commented lines, use the next, uncommitted, ones:
    // myBignumber = new web3.utils.BN(1);
    // myBignumber.add(2)
    myBignumber = new BigNumber(1); 
    myBignumber.plus(2);