gulpfile.js

var gulp = require("gulp");
var browserSync = require("browser-sync").create();
var swagger = require("swagger-parser");
var fs = require("fs");

gulp.task("serve", function() {
    browserSync.init({
        open: false,
        server: {
            baseDir: "./",
            middleware: function (req, res, next) {
                res.setHeader("Access-Control-Allow-Origin", "*");
                next();
            }
        }
    });
});

gulp.task("watch", function() {
    gulp.watch("**/*.yaml", ["build"]);
});

gulp.task("build", function() {
    swagger.dereference("swagger.yaml", function(err, api) {
        if (err) {
            console.log(err);
        } else {
            fs.writeFileSync("swagger.json", JSON.stringify(api));
        }
    });
});

gulp.task("default", ["serve", "watch"]);