How to fix NPM directory creation error?

Question

npm

npm run build-jsI run the command

"scripts": {
    "build-js": "browserify ./src/js/main.js | uglifyjs -mc > ./www/js/main.js",
  }

but if there is no www or js folder, an error pops up.
How can I make these folders create themselves if they don't exist?

Answer 1

And with the rights all the rules? Maybe they would create themselves if they could. What OS?