如何检查提取的响应是否是javascript中的json对象 [英] How to check if the response of a fetch is a json object in javascript

问题描述

我正在使用抓取polyfill从URL检索JSON或文本，我想知道如何检查响应是JSON对象还是仅文本

I'm using fetch polyfill to retrieve a JSON or text from a URL, I want to know how can I check if the response is a JSON object or is it only text

fetch(URL, options).then(response => {
   // how to check if response has a body of type json?
   if (response.isJson()) return response.json();
});

推荐答案

您可以检查响应的content-type，如

You could check for the content-type of the response, as shown in this MDN example:

fetch(myRequest).then(response => {
  const contentType = response.headers.get("content-type");
  if (contentType && contentType.indexOf("application/json") !== -1) {
    return response.json().then(data => {
      // process your JSON data further
    });
  } else {
    return response.text().then(text => {
      // this is text, do something with it
    });
  }
});

如果您需要绝对确定内容是有效的JSON(并且不信任标头)，则始终可以将响应作为text接受并自己解析:

If you need to be absolutely sure that the content is valid JSON (and don't trust the headers), you could always just accept the response as text and parse it yourself:

fetch(myRequest)
  .then(response => response.text())
  .then(text => {
    try {
        const data = JSON.parse(text);
        // Do your JSON handling here
    } catch(err) {
       // It is text, do you text handling here
    }
  });

异步/等待

如果您使用的是async/await，则可以以更线性的方式编写它:

If you're using async/await, you could write it in a more linear fashion:

async function myFetch(myRequest) {
  try {
    const reponse = await fetch(myRequest); // Fetch the resource
    const text = await response.text(); // Parse it as text
    const data = JSON.parse(text); // Try to parse it as json
    // Do your JSON handling here
  } catch(err) {
    // This probably means your response is text, do you text handling here
  }
}

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