REPL means Read-Eval-Print-Loop. It is a virtual environment that comes with Node.js. We can quickly test our JavaScript code in the Node.js REPL environment.
To launch the REPL in Node.js, just open the command prompt and type node. It will change the prompt to > in Windows and MAC.
Now we can type and run our JavaScript easily. For example, if we type 10 + 20, it will print 30 in the next line.