const tracer = ... // As previously defined
tracer.scoped(() => {
  // Previous example
  const previousResult = 404; 

  tracer.scoped(() => {
    const id = tracer.createChildId();

    tracer.setId(id);
    tracer.recordAnnotation(new zipkin.Annotation.ClientSend());
    tracer.recordAnnotation(new zipkin.Annotation.Rpc("My Child Span"));

    fetch("https://http.cat/" + previousResult).then(res => res.json()).then(result => {
      tracer.scoped(() => {
        tracer.setId(id);
        tracer.recordAnnotation(new zipkin.Annotation.ClientRecv());    
      });
    });
  });
});