react本机android错误SyntaxError:位置0处的JSON中存在意外标记

Question

错误日志：

blob:http://localhost:8081/d0cb8da3-cbda-4352-940d-9ad7827bfee6:55463 Possible Unhandled Promise Rejection (id: 0):
SyntaxError: Unexpected token  in JSON at position 0
SyntaxError: Unexpected token  in JSON at position 0
    at parse (<anonymous>)
    at tryCallOne (blob:http://localhost:8081/d0cb8da3-cbda-4352-940d-9ad7827bfee6:21859:14)
    at blob:http://localhost:8081/d0cb8da3-cbda-4352-940d-9ad7827bfee6:21960:17
    at blob:http://localhost:8081/d0cb8da3-cbda-4352-940d-9ad7827bfee6:8761:21
    at _callTimer (blob:http://localhost:8081/d0cb8da3-cbda-4352-940d-9ad7827bfee6:8650:9)
    at _callImmediatesPass (blob:http://localhost:8081/d0cb8da3-cbda-4352-940d-9ad7827bfee6:8686:9)
    at Object.callImmediates (blob:http://localhost:8081/d0cb8da3-cbda-4352-940d-9ad7827bfee6:8905:14)
    at MessageQueue.__callImmediates (blob:http://localhost:8081/d0cb8da3-cbda-4352-940d-9ad7827bfee6:8239:18)
    at blob:http://localhost:8081/d0cb8da3-cbda-4352-940d-9ad7827bfee6:8066:18
    at MessageQueue.__guardSafe (blob:http://localhost:8081/d0cb8da3-cbda-4352-940d-9ad7827bfee6:8223:11)

问题只出现在Android上，原生的react。我使用fetch，方法post。

示例代码：

fetch(config.server + "/api/districts", {
      method: "POST"
    })
      .then(res => res.json())
      .then(res => {
        this.setState({ districts: res.data });
      });

Answer 1

只是后端编码有问题(没有BOM的UTF-8)。