The lodash method _.flatten exported as a Node.js module.
_.flatten
Using npm:bash $ {sudo -H} npm i -g npm $ npm i --save lodash.flatten
bash $ {sudo -H} npm i -g npm $ npm i --save lodash.flatten
In Node.js:js var flatten = require('lodash.flatten');
js var flatten = require('lodash.flatten');
See the documentation or package source for more details.