asteroidos.org/templates/_plugins/link-checker.js

var options = {
    stage: 'render:post:page'
};

var cheerio = require('cheerio'),
    request = require('request');

var linkMap = {};

module.exports = function(params, callback) {
    'use strict';

    var page = params.page.dest.replace(params.page.dirname, "").substr(1),
        shortname = page.replace(/\/?index.html$/, "");

    // load current page content
    var $ = cheerio.load(params.content);

    // get all the anchor tags from inside the headers
    var anchors = $('h1[id],h2[id],h3[id],h4[id],h5[id],a[id]'),
        links = $('a[href]'),
        failures = [],
        externalLinks = [],
        externalLinksChecked = 0,
        syncFinished = false;

    function finish() {
        if (syncFinished && externalLinks.length === externalLinksChecked) {
            if (failures.length > 0) {
                console.log("\n");
                failures.forEach(function(error) {
                    console.log(error);
                });
                //throw new Error("failed to find some links");
            }

            callback();
        }
    }

    if (!linkMap[shortname]) {
        linkMap[shortname] = {};
    }

    linkMap[shortname].anchors = anchors.map(function(i, e) {
            return $(e).attr("id");
        });

    if (linkMap[shortname].checks) {
        linkMap[shortname].checks.map(function (check) { check(); });
    }

    function isLinkException(href, $e) {
        if (href === "#" && $e.attr("class") === "dropdown-toggle") {
            return true;
        }
        if (href === '#' && $e.attr("class") === "navbar-brand" && shortname === "") {
            //console.log("leaving '" + shortname + "'");
            return true;
        }
        return false;
    }

    links.map(function(i, e) {

        function checkInternalCrossRefLink() {
            if (!findLink(linkid, linkMap[linkpage].anchors)) {
                failures.push("Could not find internal cross link '" + href + "' as part of link '" + $.html(e) + "'");
            }
        }


        var href = $(e).attr("href");
        if (href.match(/^#/)) {
            if (!isLinkException(href, $(e))) {
                if (!findLink(href.substr(1), linkMap[shortname].anchors)) {
                    failures.push("Could not find '" + href + "' as part of link '" + $.html(e) + "'");
                }
            }
        } else if (href.match("^(https?:)?//")) {
            if (href.indexOf("http://localhost") !== 0) {
                externalLinks.push(href);
                checkLink(href, function(ok, statusCode) {
                    externalLinksChecked++;
                    if (!ok) {
                        failures.push("Could not find external '" + href + "' as part of link '" + $.html(e) + "'. Got status code " + statusCode);
                    }
                    finish();
                });
            }
        } else {
            var split = href.split("#"),
                linkpage = split[0],
                linkid = split[1],
                currentDirectory = "";

            if (page.indexOf("/") > 0) {
                currentDirectory = page.substr(0, page.indexOf("/"));
            }

            if (linkpage.indexOf("../") === 0) {
                linkpage = linkpage.substr(3);
            } else {
                linkpage = currentDirectory + "/" + linkpage;
            }

            linkpage = linkpage.replace(/(^\/)|(\/$)/g,"");

            if (linkpage !== "usage" && linkpage !== "features" && linkpage !== "" && linkpage !== "functions" && linkpage !== "about") {
                failures.push("Could not find internal page '" + href + "' as part of link '" + $.html(e));
            }

            if (linkid) {
                if (!linkMap[linkpage]) {
                    linkMap[linkpage] = {};
                }
                if (linkMap[linkpage].anchors) {
                    checkInternalCrossRefLink();
                } else {
                    linkMap[linkpage].checks = linkMap[linkpage].checks || [];
                    linkMap[linkpage].checks.push(checkInternalCrossRefLink);
                }
            }
        }
    });

    syncFinished = true;
    finish();
};

var que = [],
    activeRequests = 0;

function checkLink(link, callback) {

    if (link.indexOf("//") === 0) { link = "http:" + link; }

    if (activeRequests >= 9) {
        que.push(doRequest);
    } else {
        doRequest();
    }

    function doRequest() {
        activeRequests++;
        request.get({uri: link, strictSSL: false }, function (error, res, body) {
            if (error) {
                callback(false, error);
            } else {
                callback(res.statusCode === 200, res.statusCode);
            }
            if (que.length) {
                que.pop()();
            } else {
                activeRequests--;
            }
        });
    }
}

function findLink(linkToFind, anchors) {
    for(var i = 0; i < anchors.length; i++) {
        if (anchors[i] === linkToFind) {
            return true;
        }
    }
    return false;
}

module.exports.options = options;