![](/img/trans.png)
[英]Detecting the end of execution of an asynchronous function that provides no callback
[英]Callback after end of asynchronous recursive function
下面的功能以递归方式打印文件夹中的Chrome书签。 在处理完最后的递归循环后,如何更改下面的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了对所有内容的处理。
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);
});
});
}
编辑:对不起,我不认为我在初始代码示例中很清楚。 我已经更新了代码,通过多次调用该函数来显示异步函数存在的问题。 我想要在printBookmarks
函数调用之后等待所有printBookmarks
函数完成处理的任何代码。
您的异步方法实例可能全部一次执行,并且您不知道事先会有多少个实例。 因此,您必须保留计数,然后在完成最后一个异步方法时使用回调。
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();
});
}
我最近不得不解决这个问题。 该解决方案类似于Eric的解决方案,但是我发现我需要count变量在该函数中是局部的。 这是我要解决的方法:
for(var i=0;i<foldersArray.length; i++){
// The loop make's several call's with different folder ID's.
var printed_children = 0;
printBookmarks(foldersArray[i],function() {
printed_children++;
if(printed_children == foldersArray.length){
// You know you are done!
}
});
}
// I'd like any code here to be run only after the above has
//finished processing.
function printBookmarks(id,finished_callback) {
// the printed_children count is local so that it can keep track of
// whether or not this level of recursion is complete and should call
// back to the previous level
var printed_children = 0;
chrome.bookmarks.getChildren(id, function(children) {
children.forEach(function(bookmark) {
console.debug(bookmark.title);
// added a callback function to the printBookmarks so that it can
// check to see if all upstream recursions have completed.
printBookmarks(bookmark.id,function() {
printed_children++;
if(printed_children == children.length){
finished_callback();
}
});
});
if(children.length == 0){
finished_callback();
}
});
}
这有点难看,但应该可以。
您可以执行类似JQFAQ.com的操作 。我正在为将来的使用进行更新。
您可以将所有已完成的调用保存到变量中,并根据要处理的书签数量进行测试。 当到达末尾时(完成计数等于要处理的书签数量),然后执行最终功能。
这里有一个类似问题的答案,其中的代码可以用作指导:
可能是解决此问题的更好方法,但是您可以添加depth参数,例如
printBookmarks('0', 0);
function printBookmarks(id, depth) {
chrome.bookmarks.getChildren(id, function(children) {
children.forEach(function(bookmark) {
console.debug(bookmark.title);
printBookmarks(bookmark.id, depth + 1);
});
if(depth == 0) yourFunction();
});
}
编辑以回应评论
这是另一个答案的变体,只是方法略有不同。
runCount = 0;
for (var i = 0; i < foldersArray.length; i++) {
// The loop makes several calls with different folder IDs.
printBookmarks(foldersArray[i]);
runCount++;
}
while(runCount > 0) { // sleep for 10ms or whatnot}
// 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);
runCount--;
});
});
}
声明:本站的技术帖子网页,遵循CC BY-SA 4.0协议,如果您需要转载,请注明本站网址或者原文地址。任何问题请咨询:yoyou2525@163.com.