util 
Node.js's util module for all engines.
This implements the Node.js util module for environments that do not have it, like browsers.
Install
You usually do not have to install util yourself. If your code runs in Node.js, util is built in. If your code runs in the browser, bundlers like browserify or webpack also include the util module.
But if none of those apply, with npm do:
npm install util
Usage
var util = require('util')
var EventEmitter = require('events')
function MyClass() { EventEmitter.call(this) }
util.inherits(MyClass, EventEmitter)
Browser Support
The util module uses ES5 features. If you need to support very old browsers like IE8, use a shim like es5-shim. You need both the shim and the sham versions of es5-shim.
To use util.promisify and util.callbackify, Promises must already be available. If you need to support browsers like IE11 that do not support Promises, use a shim. es6-promise is a popular one but there are many others available on npm.
API
See the Node.js util docs. util currently supports the Node 8 LTS API. However, some of the methods are outdated. The inspect and format methods included in this module are a lot more simple and barebones than the ones in Node.js.
Contributing
PRs are very welcome! The main way to contribute to util is by porting features, bugfixes and tests from Node.js. Ideally, code contributions to this module are copy-pasted from Node.js and transpiled to ES5, rather than reimplemented from scratch. Matching the Node.js code as closely as possible makes maintenance simpler when new changes land in Node.js.
This module intends to provide exactly the same API as Node.js, so features that are not available in the core util module will not be accepted. Feature requests should instead be directed at nodejs/node and will be added to this module once they are implemented in Node.js.
If there is a difference in behaviour between Node.js's util module and this module, please open an issue!