Skip to main content

Node.js - REPL Terminal - Read Eval Print Loop

What is REPL?

The REPL stand for “Read Eval Print Loop” and The REPL module provides a “Read-Eval-Print-Loop” implementation.

                    I.            Read – Read user inputs.
                  II.            Eval – Evaluates the data structure.
                III.            Print – Print the result.
                IV.            Loop - Loops the above command until the user multiple presses.

It is also represents a computer environment likes,
                    I.            A Windows Console,
                  II.            UNIX and
                III.            Linux etc.

In Node.js, The REPL is use for JavaScript code debugging and also for experimenting etc.

It is also available for standalone or other accessible programs.


Node.js itself uses the REPL module to provide its own interactive interface for executing JavaScript and it can use by executing the Node.js binary without passing any arguments.

It is using looks like, const repl = require ('repl');

The REPL module exports from the “repl.REPLServer” class and the Instances of “repl.REPLServer” is automatically supported to,
                    I.            Completion of inputs,
                  II.            Simplistic Emacs style line editing,
                III.            Multi line inputs and
                IV.            ANSI styled output etc.

By default, all instances of “repl.REPLServer” are using an evaluation function that are evaluates JavaScript expressions and provides access to “Node.js” built in modules.

The special keys and commands are supported by REPL,

                    I.            .break – This command is use to exit from multiline expressions.
                  II.            .clear – This command is use to reset the REPL context.
                III.            .exit – This command is use to close the I/O stream.
                IV.            .help – This command is use to display the list of special commands.
                  V.            .save – This command is use to save the current REPL session.
                VI.            .load – This command is use to load a file into the current REPL session.
              VII.            .editor - This command is use to allow editor mode.
            VIII.            Ctrl + c − This command is use to terminate the current command.
                IX.            Ctrl + c twice − This command is use to terminate the Node REPL.
                  X.            Ctrl + d − terminate the Node REPL.


I hope this information will be helpful! Thank you!


By Anil Singh | Rating of this article (*****)

Popular posts from this blog

39 Best Object Oriented JavaScript Interview Questions and Answers

Most Popular 37 Key Questions for JavaScript Interviews. What is Object in JavaScript? What is the Prototype object in JavaScript and how it is used? What is "this"? What is its value? Explain why "self" is needed instead of "this". What is a Closure and why are they so useful to us? Explain how to write class methods vs. instance methods. Can you explain the difference between == and ===? Can you explain the difference between call and apply? Explain why Asynchronous code is important in JavaScript? Can you please tell me a story about JavaScript performance problems? Tell me your JavaScript Naming Convention? How do you define a class and its constructor? What is Hoisted in JavaScript? What is function overloadin

List of Countries, Nationalities and their Code In Excel File

Download JSON file for this List - Click on JSON file    Countries List, Nationalities and Code Excel ID Country Country Code Nationality Person 1 UNITED KINGDOM GB British a Briton 2 ARGENTINA AR Argentinian an Argentinian 3 AUSTRALIA AU Australian an Australian 4 BAHAMAS BS Bahamian a Bahamian 5 BELGIUM BE Belgian a Belgian 6 BRAZIL BR Brazilian a Brazilian 7 CANADA CA Canadian a Canadian 8 CHINA CN Chinese a Chinese 9 COLOMBIA CO Colombian a Colombian 10 CUBA CU Cuban a Cuban 11 DOMINICAN REPUBLIC DO Dominican a Dominican 12 ECUADOR EC Ecuadorean an Ecuadorean 13 EL SALVADOR

AngularJs input date format calendar

Table of Context bout  the input date.  Click for live demo on plnker 1. Allow to use of a custom date format like "yyyy/MM/dd" or "yyyy-MM-dd" etc. 2. Allow to check the input date typed by the user is correct or not. 1 2 3 4 //The model must be a Date object, otherwise Angular will throw an error. //The error is Invalid Date objects will be rendered as an empty string. i.e. The dates whose getTime() is NaN. //The model must be a Date object, otherwise Angular will throw an error. //The error is Invalid Date objects will be rendered as an empty string. i.e. The dates whose getTime() is NaN. The Example 1 code as given below. 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 <!doctype html> <html lang= "en" > <head>      <meta charset= "utf-8" />      <script src= " http://ajax.googleapis.com/ajax/lib

25 Best Vue.js 2 Interview Questions and Answers

What Is Vue.js? The Vue.js is a progressive JavaScript framework and used to building the interactive user interfaces and also it’s focused on the view layer only (front end). The Vue.js is easy to integrate with other libraries and others existing projects. Vue.js is very popular for Single Page Applications developments. The Vue.js is lighter, smaller in size and so faster. It also supports the MVVM ( Model-View-ViewModel ) pattern. The Vue.js is supporting to multiple Components and libraries like - ü   Tables and data grids ü   Notifications ü   Loader ü   Calendar ü   Display time, date and age ü   Progress Bar ü   Tooltip ü   Overlay ü   Icons ü   Menu ü   Charts ü   Map ü   Pdf viewer ü   And so on The Vue.js was developed by “ Evan You ”, an Ex Google software engineer. The latest version is Vue.js 2. The Vue.js 2 is very similar to Angular because Evan You was inspired by Angular and the Vue.js 2 components looks like -

nullinjectorerror no provider for httpclient angular 17

In Angular 17 where the standalone true option is set by default, the app.config.ts file is generated in src/app/ and provideHttpClient(). We can be added to the list of providers in app.config.ts Step 1:   To provide HttpClient in a standalone app we could do this in the app.config.ts file, app.config.ts: import { ApplicationConfig } from '@angular/core'; import { provideRouter } from '@angular/router'; import { routes } from './app.routes'; import { provideClientHydration } from '@angular/platform-browser'; //This (provideHttpClient) will help us to resolve the issue  import {provideHttpClient} from '@angular/common/http'; export const appConfig: ApplicationConfig = {   providers: [ provideRouter(routes),  provideClientHydration(), provideHttpClient ()      ] }; The appConfig const is used in the main.ts file, see the code, main.ts : import { bootstrapApplication } from '@angular/platform-browser'; import { appConfig } from '