升级至D3.js v5时调用d3.json出现401（未授权）错误求助

Hey there, let's break down why you're hitting that 401 Unauthorized error when switching from D3.js v4 to v5—this is a common gotcha tied to a core change in how D3 handles network requests.

The Root Cause: Fetch API vs. XMLHttpRequest #

The key difference between v4 and v5's d3.json lies in the underlying network layer:

• In v4, d3.json relied on XMLHttpRequest (XHR), which automatically sends cookies for same-origin requests. If your somedata.json depends on session cookies or authenticated tokens stored in the browser, XHR would pass these along by default, letting your server validate your request successfully.
• In v5, D3 switched to using the Fetch API, which has a different default behavior: it does not send cookies (or other credentials) unless explicitly told to. That's why your previously working request suddenly fails with a 401—your server isn't receiving the credentials it needs to authorize you.

Fix: Add Credentials to Your d3.json Call #

To resolve this, you just need to pass a configuration object to d3.json that includes the credentials option. Here's how to update your v5 code:

var url = "somedata.json";
d3.json(url, { credentials: 'same-origin' })
  .then(function(data) {
    console.log(data);
  })
  .catch(function(error) {
    console.error('Failed to load data:', error);
  });

A quick breakdown of the valid credentials values:

• 'same-origin': Sends cookies only for requests to the same domain (this is the most common choice for your scenario)
• 'include': Sends cookies even for cross-origin requests (only use this if your server is configured to allow CORS with credentials)
• 'omit': The default behavior—no credentials are sent (which is what caused your 401 error)

Additional Debugging Tips #

• Always add a .catch() handler to your v5 Promise-based calls: This will give you more detailed error context beyond just the 401 status code.
• Use your browser's dev tools (Network tab) to compare request headers from v4 vs. v5: You'll likely notice the missing cookie in the v5 request before applying the fix.
• Double-check your server's auth logic: Ensure it's correctly handling requests from the Fetch API (though the credentials fix should resolve most cases).

内容的提问来源于stack exchange，提问作者Michael Larson