未捕获（在promise中）SyntaxError：JSON输入的意外结束 [英] Uncaught (in promise) SyntaxError: Unexpected end of JSON input

问题描述

我正在尝试向我的服务器发送新的推送订阅，但遇到错误未捕获（在承诺中）SyntaxError：JSON输入的意外结束并且控制台说它在我的索引页面的第1行，显然是不是这样。

I am trying to send a new push subscription to my server but am encountering an error "Uncaught (in promise) SyntaxError: Unexpected end of JSON input" and the console says it's in my index page at line 1, which obviously is not the case.

我怀疑发生问题的函数（因为我发表评论时没有抛出错误）是 sendSubscriptionToBackEnd（订阅） 在以下内容中调用：

The function where I suspect the problem occurring (because error is not thrown when I comment it out) is sendSubscriptionToBackEnd(subscription) which is called in the following:

function updateSubscriptionOnServer(subscription) {
  const subscriptionJson = document.querySelector('.js-subscription-json');
  const subscriptionDetails = document.querySelector('.js-subscription-details');

  if (subscription) {
    subscriptionJson.textContent = JSON.stringify(subscription);
    sendSubscriptionToBackEnd(subscription);
    subscriptionDetails.classList.remove('is-invisible');
  } else {
    subscriptionDetails.classList.add('is-invisible');
  }
}

函数本身（在上述函数之前）：

The function itself (which precedes the above function):

 function sendSubscriptionToBackEnd(subscription) {
  return fetch('/path/to/app/savesub.php', {
    method: 'POST',
    headers: {
      'Content-Type': 'application/json'
    },
    body: JSON.stringify(subscription)
  })
  .then(function(response) {
    if (!response.ok) {
      throw new Error('Bad status code from server.');
    }

    return response.json();
  })
  .then(function(responseData) {
    if (!(responseData.data && responseData.data.success)) {
      throw new Error('Bad response from server.');
    }
  });
}

我试过在fetch调用中用双引号替换单引号但是产生了相同的结果。

I have tried replacing single quotes with double quotes in the fetch call but that yields the same results.

我知道应填充JSON，因为它会在 updateSubscriptionOnServer（）函数与 subscriptionJson.textContent = JSON.stringify（subscription）; ，我在google codelab的示例服务器中使用该输出成功接收推送。

I know that the JSON should be populated because it prints to the screen in the updateSubscriptionOnServer() function with subscriptionJson.textContent = JSON.stringify(subscription);, and I used that output in the google codelab's example server to receive a push successfully.

编辑：这是JSON作为字符串，但我没有看到语法错误：

Here is the JSON as a string, but I don't see a mistake in syntax:

{"endpoint":"https://fcm.googleapis.com/fcm/send/dLmthm1wZuc:APA91bGULRezL7SzZKywF2wiS50hXNaLqjJxJ869y8wiWLA3Y_1pHqTI458VIhJZkyOsRMO2xBS77erpmKUp-Tg0sMkYHkuUJCI8wEid1jMESeO2ExjNhNC9OS1DQT2j05BaRgckFbCN","keys":{"p256dh":"BBz2c7S5uiKR-SE2fYJrjPaxuAiFiLogxsJbl8S1A_fQrOEH4_LQjp8qocIxOFEicpcf4PHZksAtA8zKJG9pMzs=","auth":"VOHh5P-1ZTupRXTMs4VhlQ=="}}

任何想法??

推荐答案

这可能是端点没有在响应标题中传递适当参数的问题。

This might be a problem with the endpoint not passing the appropriate parameters in the response's header.

在Chrome中控制台，在网络选项卡内，检查端点发送的标头，它应包含：
允许来自localhost和跨域请求的请求的正确响应示例

In Chrome's console, inside the Network tab, check the headers sent by the endpoint and it should contain this: Example of proper response to allow requests from localhost and cross domains requests

请API开发人员将其包含在标题中：

Ask the API developer to include this in the headers:

"Access-Control-Allow-Origin" : "*", 
"Access-Control-Allow-Credentials" : true 

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