# Next.js fetch API error

- https://vercel.com/docs/projects/environment-variables/system-environment-variables
- https://laros.io/how-to-get-the-current-url-with-nextjs-on-vercel

fetch 了全部的URL：`https://docs-vector-search-demo.vercel.app/api/vectorSearch`，错误的使用是只有 `/api/vectorSearch` 。

一个 work 的步骤：

1. 在 Vercel 设置环境变量：=NEXT_PUBLIC_URL=https://$NEXT_PUBLIC_VERCEL_PROJECT_PRODUCTION_URL=
2. 本地环境变量 .env.development:

```
NEXT_PUBLIC_URL=http://localhost:3000
```

3.  使用 dotenv-expand 处理

```bash
npm install dotenv-expand
```

```javascript
// next.config.js

const dotenvExpand = require("dotenv-expand");

dotenvExpand.expand({ parsed: { ...process.env } });

// The rest of your config
```

4.  最终效果

```bash
console.log(process.env.NEXT_PUBLIC_URL);

// Output localhost: http://localhost:3000
// Output preview: https://random-url.vercel.app
// Output production: https://your-website.com
```


相关：[[cannot-use-ejs|cannot-use-ejs]]