Promise.filter

html2json.js

var listTree = FS.listTree("../../data/", function isIndexHTML(filePath, stat) {
    if (stat.isDirectory()) {
        return false;
    }
    return path.basename(filePath) === "index.html";
}).then(function (fileList) {
    var promiseMap = Promise.filter(fileList, function (filePath) {
        return FS.exists(path.join(path.dirname(filePath), "index.json")).then(function(result){
            return !result;
        });
    });
    return Promise.all(promiseMap).then(function (res) {
        console.log(res);
    });
});