问带有标志变量的递归和异步方法

EN

// utility: runs an ajax request and handles errors on the low level
function ajax(options) {
    return $.ajax(options).fail(function(jqXHR, textStatus, errorThrown) {
        console.log(textStatus, errorThrown, jqXHR);
    });
}

// utility: makes paged Ajax requests through a worker function
function pagedAjax(ajaxFunc, items, pageSize) {
    var temp = [].slice.call(items), page,
        requests = [];

    // start as many parallel Ajax requests as we have pages
    while (temp.length) {
        page = temp.splice(0, pageSize);
        requests.push( ajaxFunc(page) );
    }

    // wait until all requests have finished, return combined result
    return $.when.apply($, requests).then(function (results) {
        var combined = [];
        $.each(results, function (i, result) {
            // result is an array [data, textStatus, jqXhr]
            // push all contained items onto combined
            // (the following assumes that data is an array of objects)
            [].push.apply(combined, result[0]);
        });
        return combined;
    });
}

// worker: retrieves a list of article IDs from topic IDs
function getSuggestedArticles(topics) {
    return ajax({method: 'post', url: '/articlesByTopic', data: topics});
    // or whatever API request returns a list of articles IDs from topic IDs
}

// worker: takes a list of article IDs, returns a list of _unread_ article IDs
function getUnvisitedArticles(articles) {
    return ajax({method: 'post', url: '/unvisitedArticles', data: articles});
    // or whatever API request returns a list of unvisited articles from IDs
}

// worker: takes a list of article IDs, returns a list of articles
function fillWithContent(articles) {
    return ajax({method: 'post', url: '/articles', data: articles});
    // or whatever API request fills articles with content
}

// takes a list of topic IDs, requests article IDs, filters them, returns actual articles
function getUnvisitedArticlesByTopic(topicIds) {
    var pageSize = 100;

    return pagedAjax(getSuggestedArticles, topicIds, pageSize)
        .then(function (allArticles) {
            return pagedAjax(getUnvisitedArticles, allArticles, pageSize);
        })
        .then(function (unvisitedArticles) {
            return pagedAjax(fillWithContent, unvisitedArticles, pageSize);
        });
}

// renders unvisited articles 
function renderUnvisitedArticles() {
    var topicIds = [9, 1500, 745];

    getUnvisitedArticlesByTopic(topicIds).done(function (articles) {
        $.each(articles, function (i, article) {
            // show article on page
        });
    });
}