javascript-dev-demo/gulpfile.js

const { src, dest, series } = require("gulp");
const concat = require("gulp-concat");
const watch = require("gulp-watch");

function buildTask() {
    return src(["src/**/*.js"]).pipe(concat("dec.plugin.demo.js")).pipe(dest("./dist"));
}

function watchTask() {
    return watch(["src/**/*.js"], buildTask)
}

exports.buildTask = buildTask;
exports.devTask = series(buildTask, watchTask);