gulp + browserify

gistfile1.js

var gulp = require('gulp');
var browserify = require('browserify');
var source = require('vinyl-source-stream');

var libs = ["underscore", "jquery"];

gulp.task("vendor", function () {
  var b = browserify();

  libs.forEach(function (lib) {
    b.require(lib);
  });

  return b.bundle()
    .pipe(source("vendor.js"))
    .pipe(gulp.dest('./build/'));
});

gulp.task("app", function () {
  var b = browserify({entries:"./app.js"});

  libs.forEach(function (lib) {
    b.external(lib);
  });

  return b.bundle()
    .pipe(source("app.js"))
    .pipe(gulp.dest('./build/'));
});