A typescript function to truncate a potentially circular structure to a finite depth

finiteDepth.ts

// Takes a structure with possible circular references, e.g.
// functions.https.CallableContext, and truncates it to finite depth.
function finiteDepth(x: any, depth: bigint): any {
    if (depth <= 0) {
        return "Truncated by finiteDepth"
    } else if (x instanceof Array) {
        return x.map(e => finiteDepth(e, depth - 1n))
    } else if (typeof x === 'object' && x !== null) {
        return Object.fromEntries(
            Object.entries(x).map(
                ([k, v]) => [k, finiteDepth(v, depth - 1n)]))
    } else {
        return x
    }
}