React response from fetch as json

Question

The fetch statement getting json data from the server. I want to get the value of the object to be saved in state. The response is only one element in it [{"QuestId":1700}]. How to get the value of QuestId. My code is giving error of undefined.

fetch("http://testapi/quest", {
      .then(res => res.json())
      .then(
        res => {
          setQuestId(JSON.stringify(res.QuestId))
          console.log('Test' + qid);
        },
        (error) => {
          alert("Failed" + error);
        }
      );

Answer 1

If res has a value of [{"QuestId":1700}], then it's an array; if you're sure you want to get the first entry, you have to do res[0].QuestId instead of res.QuestId. The error is somewhat indicative - an array doesn't have a property QuestId.