gulpfile.js

gulp.task("js:crypto", function() {
  var browserify = require("browserify");
  var source = require("vinyl-source-stream");
  var b = browserify({
    basedir: "./"
  });
  b.require("crypto", {expose: "crypto"});
  return b.bundle()
    .pipe(source("crypto.js"))
    .pipe(gulp.dest(jsOutPath));
});