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

问题描述

以下的功能打印Chrome书签文件夹中递归。我怎么可能会改变这个函数的调用另一个函数的最后递归循环处理后？ chrome.bookmarks.getChildren（）是异步的，这使得当函数处理完一切很难知道。

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.

感谢。

    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);
           });
        });
    }

编辑：对不起，我不认为我是在初始code例子清楚。我已经更新了code。通过多次调用该函数来显示我与异步函数有问题。我想在 printBookmarks 功能后的任何code调用等待所有的 printBookmarks 函数来完成处理

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

您异步方法实例可以一次全部被执行，而你不知道有多少会有事前。所以，你必须保持计数，然后使用回调当最后一个异步方法完成。

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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