javascript - 在回调中调用异步函数

Question

这个问题已经有答案了:

Chrome Extension Message passing: response not sent (4 个回答)

已关闭 8 年前。

我的background.js中有这段代码:

chrome.extension.onMessage.addListener( function(request,sender,sendResponse){
    chrome.tabs.query({active: true, currentWindow: true}, function(tabs){
        var requests = getTabRequests(tabs[0].id);
                //getTabRequests gets all the information i stored about a tab
        sendResponse( {requests: requests});
    });
 });

我想要它做的是响应 popup.js。 chrome.tabs.query这对我来说是不可能的。我意识到这是一个异步函数，但是如何修复它呢？或者是不发送响应的唯一可能性，而只是在不同方向发送另一条消息(这意味着我无法使用 mu popup.js 中的回调函数)

Answer 1

阅读 chrome.runtime.onMessage 的文档:

function sendResponse
Function to call (at most once) when you have a response. The argument should be any JSON-ifiable object. If you have more than one onMessage listener in the same document, then only one may send a response. This function becomes invalid when the event listener returns, unless you return true from the event listener to indicate you wish to send a response asynchronously (this will keep the message channel open to the other end until sendResponse is called).

chrome.runtime.onMessage.addListener(function(request, sender, sendResponse){
    chrome.tabs.query({active: true, currentWindow: true}, function(tabs){
        var requests = getTabRequests(tabs[0].id);
        //getTabRequests gets all the information i stored about a tab
        sendResponse({requests: requests});
    });
    <b>return true; // <-- Required if you want to use sendResponse asynchronously!</b>
 });

(chrome.extension.onMessage 已弃用，请使用 chrome.runtime.onMessage 代替，但前者是后者的别名。)