What is the difference between JavaScript Engine and JavaScript Runtime Environment

Question

I'm feeling a bit confused, could someone help to describe What is the difference between JavaScript Engine and JavaScript Runtime Environment. BTW, Event Loop was implemented in Engine or Runtime?

Answer 1

Unlike C and other compiled languages, Javascript runs in a container - a program that reads your js codes and runs them. This program must do two things

• parse your code and convert it to runnable commands
• provide some objects to javascript so that it can interact with the outside world.

The first part is called Engine and the second is Runtime.

For example, the Chrome Browser and node.js use the same Engine - V8, but their Runtimes are different: in Chrome you have the window, DOM objects etc, while node gives you require, Buffers and processes.

Answer 2

Imagine a robot is playing a music:

• The JavaScript code would be the music notes to the robot.
• TheJavaScript engine would be the robot which can understand the notes and act on it.
• The JavaScript runtime would be the instruments the robot can use in order to play the music.

Imagine a robot is putting out a fire:

• The JavaScript code would be the instructions to the robot to put out a fire.
• The JavaScript engine would be the robot which can understand the instructions and act on it.
• The JavaScript runtime would be the fire truck, and the water gun.