javascript - "Return"来自函数未分配给变量

Question

我编写了一个函数，它递归地搜索一个对象以从中获取所有特定元素，并返回结果元素数组。

函数本身工作得很好，但由于某种原因，“返回”部分的结果没有分配给调用该函数的变量。

这是函数本身:

var getLinksInObject = function(object){
    // Define Variables
    var allLinks = [];
    var getLinksTimeout = null;

    // Function to get the links in an object. Called recursively
    var getLinks = function(object){
        // Get category and link links
        var categories = object.categories;
        var links = object.links;

        // If there are links
        if (links && links.length > 0){
            // Push each of them to the allLinks array
            for (var i=0, j=links.length; i<j; i++){
                allLinks.push(links[i]);
            };
        };

        // If there are category links, push them to the allLinks array
        if (categories && categories.length > 0){
            for (var i=0, j=categories.length; i<j; i++){
                // Build the link
                var link = {
                    title: categories[i].title,
                    link: categories[i].link
                };
                // Push the link to allLinks
                allLinks.push(link);

                // If there are sub-links, run getLinks on that object to get the next level of links
                if (categories[i].categories) {
                    // Reset the listener so it knows we are going for another round
                    resetTimeout();

                    // Get the links in the next level
                    getLinks(categories[i]);
                }           
            };
        };
    };

    // Listens for when the recursive calls finish and returns the result
    var resetTimeout = function(){
        clearTimeout(getLinksTimeout);
        getLinksTimeout = setTimeout(function(){
            log(allLinks);
            return allLinks;
        }, 50);
    };

    resetTimeout();
    getLinks(object);
};

这是一个运行它的测试对象，它与实际对象的结构相匹配:

{
    link: "http://test.com",
    title: "This is a test",
    categories: [
        {
            link: "http://test.com",
            title: "This is a test",
            categories: [
                {
                    link: "http://test.com",
                    title: "This is a test",
                    categories: [
                        {

                        }
                    ]
                }
            ]
        },
        {
            link: "http://test.com",
            title: "This is a test",
            categories: [
                {
                    link: "http://test.com",
                    title: "This is a test",
                    categories: [
                        {
                            link: "http://test.com",
                            title: "This is a test",
                            categories: [
                                {
                                    link: "http://test.com",
                                    title: "This is a test"
                                }
                            ]
                        }
                    ]
                },
                {
                    link: "http://test.com",
                    title: "This is a test",
                    categories: [
                        {

                        }
                    ]
                },
                {
                    link: "http://test.com",
                    title: "This is a test",
                    categories: [
                        {

                        }
                    ]
                }
            ]
        },
        {
            link: "http://test.com",
            title: "This is a test",
            categories: [
                {
                    link: "http://test.com",
                    title: "This is a test",
                    categories: [
                        {

                        }
                    ]
                }
            ]
        }
    ]
}

这是一个重复问题的 fiddle 。您将能够在控制台中看到问题，因为“结果”的日志记录被注销为未定义。

http://jsfiddle.net/KS7LG/

Answer 1

您分配给 getLinksInObject 的函数没有 return 语句。它将始终返回未定义。

整个代码中唯一的return语句是这样的:

setTimeout(function(){
console.log(allLinks);
    return allLinks;
}, 50);

该函数由 setTimeout 调用，并且 setTimeout 不关注它调用的函数的任何返回值。

setTimeout 是异步的，它稍后运行代码并且不会阻止调用它的函数继续。如果你想处理时间用完后生成的数据，那么你必须从你传递的函数继续这样做，再将数据传回去就太晚了。