Path builder for a propety accessor function

as-path.ts

interface Accessor<T, U> {
	(state: T): U;
}

function property_access(p: string, optionally_chained: boolean): string {
    let result = p;
    const letter_start = /^[A-Za-z]/.test(p);
    if (!letter_start) {
        if (!/^\d+$/.test(p)) {
            result = `'${ result }'`
        }
        result = `[${ result }]`;
    }
    if (letter_start || optionally_chained) {
        result = `.${ result }`;
    }
    if (optionally_chained) {
        result = `?${ result }`;
    }
    return result;
}

function asPath(accessor: Accessor<any, unknown>): string {
    let path = '';
    let leaf = {} as any;
    let optionally_chained: boolean;

    accessor(new Proxy(leaf, {
        get(tree, p: string, r) {
            path += path ? property_access(p, optionally_chained) : p;
            try {
                accessor(tree);
                optionally_chained = true;
            } catch (_) {
                optionally_chained = false;
            }
            leaf = leaf[p] = {};
            return r;
        }
    }));
    return path;
}

usage.ts

const deep = (state: any) => state?.g.h.i?.j;
const accessor = (state: any) => deep(state.a?.b?.[1]?.c.d['->'].e.f);

const path = asPath(accessor);

console.log(path) // a?.b?.[1]?.c.d['->'].e.f?.g.h.i?.j