Javascript 在异步存储函数中运行函数无法完成回调

所以我想用从存储器中提取的数据来响应请求。不知道为什么这段代码可以工作，但无论如何，我知道如何删除注释下的警报，这样我就不会有一个空的弹出窗口，这仍然可以工作

background.js:

var mData = [];
chrome.runtime.onMessage.addListener(function(request, sender, sendResponse){
  if (request.command == "submit-chat") { 
    chrome.tabs.getSelected(null, function(tab) {
      chrome.tabs.executeScript(tab.id, {code: "chat.send_message();"});
    });
  } else if (request.command == "set-emots"){
    var data = {};
    request.emots.forEach(function(entry) {
      var emot = JSON.parse(entry);
      data[emot.alt] = JSON.stringify(entry);
    });
    chrome.storage.sync.clear();
    chrome.storage.sync.set(data);
  } else if (request.command == "get-emots"){
    //Not sure why the alert is needed it is like it lets the sendResponce out of the function
    alert(chrome.storage.sync.get(null, function(result){
      if (!result) {
        getPage();
      } else {
        Object.keys(result).forEach(function(entry) {
          mData.push(result[entry]);
        });
      }
      sendResponse({emots: mData.join("|≈|")});
    }));
  } 
});

它被称为什么地方

content.js

var emoticons = null;
window.onload = function(){
    jQuery.noConflict();
    chrome.runtime.sendMessage({command: "get-emots"}, function(response) {
        emoticons = response.emots;
        if (emoticons !== null) { 
            var input = document.getElementsByClassName("input")[0].innerHTML = "";
            jQuery(".input").load(chrome.extension.getURL("input.html"), function(){...});
            }
    });
}

function getPage(){
  alert("You are going to be redirected to a page to get all hipchat emoticons. Please refresh that page then come back and refresh this page.");
  var win = window.open('http://hipchat-emoticons.nyh.name', '_blank');
  win.focus();
};

var getEmots = function(callback){
    chrome.storage.sync.get(null, function(result){
      if (!result) {
        getPage();
      } else {
        Object.keys(result).forEach(function(entry) {
          mData.push(result[entry]);
        });
      }
      typeof callback === 'function' && callback(mData);
    });
};

var mData = [];
chrome.runtime.onMessage.addListener(function(request, sender, sendResponse){
  if (request.command == "submit-chat") { 
    chrome.tabs.getSelected(null, function(tab) {
      chrome.tabs.executeScript(tab.id, {code: "chat.send_message();"});
    });
  } else if (request.command == "set-emots"){
    var data = {};
    request.emots.forEach(function(entry) {
      var emot = JSON.parse(entry);
      data[emot.alt] = JSON.stringify(entry);
    });
    chrome.storage.sync.clear();
    chrome.storage.sync.set(data);
  } else if (request.command == "get-emots"){
    getEmots(function(mData){ sendResponse({emots: mData.join("|≈|")}); });
    return true;
  } 
});

更新：所以我尝试了这个，但仍然没有成功

var getEmots = function(callback){
    chrome.storage.sync.get(null, function(result){
      if (!result) {
        getPage();
      } else {
        Object.keys(result).forEach(function(entry) {
          mData.push(result[entry]);
        });
      }
      typeof callback === 'function' && callback(mData);
    });
};

var mData = [];
chrome.runtime.onMessage.addListener(function(request, sender, sendResponse){
  if (request.command == "submit-chat") { 
    chrome.tabs.getSelected(null, function(tab) {
      chrome.tabs.executeScript(tab.id, {code: "chat.send_message();"});
    });
  } else if (request.command == "set-emots"){
    var data = {};
    request.emots.forEach(function(entry) {
      var emot = JSON.parse(entry);
      data[emot.alt] = JSON.stringify(entry);
    });
    chrome.storage.sync.clear();
    chrome.storage.sync.set(data);
  } else if (request.command == "get-emots"){
    getEmots(function(mData){
      console.log("Data: " + mData);
      sendResponse({emots: mData.join("|≈|")});
    });
  } 
});

更新2:让它在这里工作是其他人的最终选择。谢谢大家，这里是决赛

这是

background.js

var emoticons = null;
window.onload = function(){
    jQuery.noConflict();
    chrome.runtime.sendMessage({command: "get-emots"}, function(response) {
        emoticons = response.emots;
        if (emoticons !== null) { 
            var input = document.getElementsByClassName("input")[0].innerHTML = "";
            jQuery(".input").load(chrome.extension.getURL("input.html"), function(){...});
            }
    });
}

function getPage(){
  alert("You are going to be redirected to a page to get all hipchat emoticons. Please refresh that page then come back and refresh this page.");
  var win = window.open('http://hipchat-emoticons.nyh.name', '_blank');
  win.focus();
};

var getEmots = function(callback){
    chrome.storage.sync.get(null, function(result){
      if (!result) {
        getPage();
      } else {
        Object.keys(result).forEach(function(entry) {
          mData.push(result[entry]);
        });
      }
      typeof callback === 'function' && callback(mData);
    });
};

var mData = [];
chrome.runtime.onMessage.addListener(function(request, sender, sendResponse){
  if (request.command == "submit-chat") { 
    chrome.tabs.getSelected(null, function(tab) {
      chrome.tabs.executeScript(tab.id, {code: "chat.send_message();"});
    });
  } else if (request.command == "set-emots"){
    var data = {};
    request.emots.forEach(function(entry) {
      var emot = JSON.parse(entry);
      data[emot.alt] = JSON.stringify(entry);
    });
    chrome.storage.sync.clear();
    chrome.storage.sync.set(data);
  } else if (request.command == "get-emots"){
    getEmots(function(mData){ sendResponse({emots: mData.join("|≈|")}); });
    return true;
  } 
});

---

由于Javascript是单线程的，异步回调在UI到达空闲循环之前不会运行。您对

alert（）

的调用会在等待用户关闭弹出窗口时强制其空闲，从而允许异步代码运行。如果getPage（）是异步的，@Barmar是正确的。您需要使用承诺或某种回调来替换警报。我尝试使用回调，但没有运行

sendResponse（{emots:mData.join（“）|≈|")});

但是它确实运行了

控制台.log（“数据：+mData）；

看到这个答案：在调用

getEmots

之后，您需要返回

true

。谢谢，这一切都非常有帮助