id object created 1 model choices delta content ! index 0 finish_reason null 用js代码提取上面这段json里的content字段里的值

const json = {
  "id": "",
  "object": "",
  "created": 1,
  "model": "",
  "choices": [{
    "delta": {
      "content": "!"
    },
    "index": 0,
    "finish_reason": null
  }]
};
const contentValue = json.choices[0].delta.content;
console.log(contentValue); // "!"