[Ethereum] how to deal with bytes32 to string in javascript

Pass it as a string "0x3fd54831f488a22b28398de0c567a3b064b937f54f81739ae9bd545967f3abab" It won't get truncated.

If this not solve read this: passing String object with "0x.." value as bytes32 to a solidity function

In Javascript, the maximum safe integer is 2^53-1.

So you should generally avoid using numbers like 100000000000000000000.

For example, in your code, you should change this:

myToken.transfer(acc[3], 100000000000000000000, {from:acc[0]})

To this:

myToken.transfer(acc[3], "100000000000000000000", {from:acc[0]})

In addition to that, the usage of toNumber() is also unsafe, as you have noticed yourself.

When you call from the off-chain an on-chain function which returns uint256, you get a BigNumber object. If this object represents a number smaller than Number.MAX_SAFE_INTEGER, then it is safe to use toNumber() on it. But since you do not know that for sure, you should avoid using toNumber().

Also, please note that it is better to use toFixed() than toString(), because the latter may return the scientific notation of the number (e.g. 1+e18), which may give you unexpected problems when you later use it in other contexts.