跨域调试bug

跨域调试bug 产品分类：uniCloud/支付宝小程序云

示例代码：

<script>
async function fetchDatasetFields() {
const cloudFunctionName = 'cs'; // 可替换为任意云函数名，如 POST_auth
const url = `https://env-*****.dev-hz.cloudbasefunction.cn/${cloudFunctionName}`;

  const payload = {  
    dataset: "users"  // 模拟参数，根据需求自定义  
  };  

  try {  
    const response = await fetch(url, {  
      method: 'POST',  
      headers: {  
        'Content-Type': 'application/json'  
      },  
      body: JSON.stringify(payload)  
    });  

    const data = await response.json();  
    document.getElementById('result').textContent = JSON.stringify(data, null, 2);  
  } catch (error) {  
    document.getElementById('result').textContent = '请求出错：' + error;  
  }  
}
</script>

操作步骤：

'use strict';

exports.main = async (event, context) => {
// 获取 HTTP 方法
const method = event.httpMethod;  

// 获取请求头和参数
const headers = event.headers;
const queryParams = event.queryStringParameters;
const body = event.body;
const isBase64Encoded = event.isBase64Encoded;  

// 如果是预检请求，直接返回 CORS 头
if (method === 'OPTIONS') {
return {
statusCode: 204,
headers: {
'Access-Control-Allow-Origin': '*',
'Access-Control-Allow-Methods': 'GET, POST, OPTIONS',
'Access-Control-Allow-Headers': 'Content-Type'
},
body: ''
};
}

// 正常处理 POST 请求
if (method === 'POST') {
// 如果 body 是 Base64 编码的，需要解码
const parsedBody = isBase64Encoded ? Buffer.from(body, 'base64').toString('utf-8') : body;  

return {  
  statusCode: 200,  
  headers: {  
    'Access-Control-Allow-Origin': '*',  
    'Access-Control-Allow-Methods': 'GET, POST, OPTIONS',  
    'Access-Control-Allow-Headers': 'Content-Type'  
  },  
  body: JSON.stringify({  
    msg: '成功',  
    received: parsedBody // 返回收到的请求体  
  })  
};
}

// 其他类型请求默认返回错误
return {  
statusCode: 400,  
body: JSON.stringify({ error: 'Unsupported HTTP method' })
};
};

预期结果：

{
"statusCode": 200,
"headers": {
"Access-Control-Allow-Origin": "*",
"Access-Control-Allow-Methods": "GET, POST, OPTIONS",
"Access-Control-Allow-Headers": "Content-Type"
},
"body": "{\"msg\":\"成功\",\"received\":\"{\\"dataset\\":\\"users\\"}\"}"
}

实际结果：

Access to fetch at 'https://env-***.dev-hz.cloudbasefunction.cn/cs' from origin 'http://127.0.0.1:8000' has been blocked by CORS policy: Response to preflight request doesn't pass access control check: No 'Access-Control-Allow-Origin' header is present on the requested resource. If an opaque response serves your needs, set the request's mode to 'no-cors' to fetch the resource with CORS disabled.

(索引):43   
        
        POST https://env-***.dev-hz.cloudbasefunction.cn/cs net::ERR_FAILED  
        
fetchDatasetFields @ (索引):43
onclick @ (索引):29