The spec in https://github.com/estree/estree/blob/master/es2020.md states

bigint property is the string representation of the BigInt value. It doesn't include the suffix n.

Should this represent the source text or a normalized notation?

In other words; is the AST for 1048575n equivalent to that of 0xfffffn or not due to the .bigint field?

get rewritten into

[
    1,
    2
]

which is not what one would expect rewriting the code. That's a small, innocent literal array. And yet I see no way to make escodegen output such lists as [1, 2]. Could you add it as a default behaviour and an option, please?

Second Example in the README.md: Shouldn't it be "return this.break();" instead of only "this.break();" in order for the traversal to end at the first node?

In a few places in the code, assert is require'd and used to throw a simple error.

You should remove this and simply 'throw new Error(...)'. The benefit of doing so is that it shrinks the browserify'd library considerably.