Trace property access in nested JavaScript objects

trace-property-access.js

const tracePropertyAccess = (obj, handler, path) => {
  path = path || [];

  return new Proxy(obj, {
    get(target, propKey, receiver) {
      const val = Reflect.get(target, propKey, receiver),
        newPath = path.concat(propKey);

      if (val && typeof val === 'object') {
        return tracePropertyAccess(val, handler, newPath);
      }

      handler.call(null, newPath);

      return val;
    }
  });
};

usage.md

const testObj = { a: 1, b: { a: "no", b: "yes" }, c: { a: "green", b: { a: "blue", b: "orange" } } };

const tracer = tracePropertyAccess(testObj, console.log);

tracer.b.a; // Prints ["b", "a"]
tracer.a; // Prints ["a"]
tracer.c.c.a; // Prints ["c", "c"]

Thanks @NinaScholz for the snippet at StackOverflow.