api.js

function checkStatus(response) {
  return new Promise((resolve, reject) => {
    const json = response.json();

    // [200,299]
    if (response.ok) {
      return json.then(resolve, reject);
    }
    if(response.status !== 200){
      alert("接口请求失败！")
    }
    json.then(reject);
  });
}

export default function fetch(input, init) {
  if (!init) {
    init = {};
  }

  init.headers = {
    'Content-Type': 'application/json',
    ...init.headers
  };

  return window.fetch(`/${input}`, init).then(checkStatus);
}