异步递归函数结束后的回调 [英] Callback after end of asynchronous recursive function

问题描述

下面的函数递归打印文件夹中的 Chrome 书签.在处理最终递归循环后，如何更改以下函数以调用另一个函数?chrome.bookmarks.getChildren() 是异步的，这使得很难知道函数何时完成处理所有内容.

The function below prints Chrome bookmarks in a folder recursively. How could I alter the below function to call another function after the final recursive loop is processed? chrome.bookmarks.getChildren() is asynchronous which makes it difficult to know when the function is done processing everything.

谢谢.

    for (var i = 0; i < foldersArray.length; i++) {
        // The loop makes several calls with different folder IDs.
        printBookmarks(foldersArray[i]);  
    }

    // I'd like any code here to be run only after the above has 
    //finished processing    

    function printBookmarks(id) {
        chrome.bookmarks.getChildren(id, function(children) {
           children.forEach(function(bookmark) { 
               console.debug(bookmark.title);
               printBookmarks(bookmark.id);
           });
        });
    }

抱歉，我认为我在最初的代码示例中没有说清楚.我已经更新了代码，通过多次调用该函数来显示我在使用异步函数时遇到的问题.我希望 printBookmarks 函数调用后的任何代码等待所有 printBookmarks 函数完成处理.

Sorry, I don't think I was clear in the initial code example. I've updated the code to show the problem I'm having with the asynchronous function by calling the function multiple times. I'd like any code after the printBookmarks function calls to wait for all the printBookmarks functions to finish processing.

推荐答案

你的异步方法实例可能都在一次执行，你事先不知道会有多少.因此，您必须保持计数，然后在最后一个异步方法完成时使用回调.

Your asynchronous method instances may all be executing at once, and you don't know how many there will be beforehand. So, you'll have to keep count and then use a callback when the last asynchronous method is done.

for (var i = 0; i < foldersArray.length; i++) {
    // The loop makes several calls with different folder IDs.
    printBookmarks(foldersArray[i], thingsToDoAfter);
}

function thingsToDoAfter() {
    // I'd like any code here to be run only after the above has 
    // finished processing.
}

var count = 0;

function printBookmarks(id, callback) {
    count++;
    chrome.bookmarks.getChildren(id, function(children) {
        children.forEach(function(bookmark) { 
            console.debug(bookmark.title);
            printBookmarks(bookmark.id, callback);
        });
        count--;
        if (count === 0 && callback)
            callback();
    });
}

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