how to run javascript in terminal with code examples

Javascript is a popular programming language that is often used in web development. However, it can also be used to write scripts that can be run on your computer's terminal. Running Javascript in terminal can be useful for tasks such as automating repetitive tasks, batch processing or simply testing small code snippets. In this article, we will explore how to run Javascript in terminal with code examples.

  1. Installing Node.js
    To run Javascript in your terminal, you will first need to install Node.js on your computer. Node.js is a runtime environment for Javascript that allows the language to be used outside of the browser. It can be installed on various operating systems, including Windows, macOS and Linux. You can download the Node.js installer from the official website and follow the instructions to install it on your computer.

Once installed, you can verify that Node.js is working correctly by opening your terminal and entering the command:

node --version

This should display the version number of Node.js that you have installed.

  1. Running Javascript files in terminal
    After installing Node.js, you can run Javascript files directly in your terminal. To do so, create a new file with a .js extension and write some Javascript code in it.

For example, let's create a file called "hello.js" and add the following code:

console.log("Hello, world!");

To run this file, navigate to the directory where it is stored in your terminal and enter the command:

node hello.js

This should output "Hello, world!" to your terminal.

  1. Passing arguments to Javascript scripts
    You can also pass arguments to your Javascript scripts when running them in terminal. These arguments can be accessed in your script using the "process.argv" array.

For example, let's modify our "hello.js" script to accept a name as an argument and print a customized greeting:

const name = process.argv[2];
console.log(`Hello, ${name}!`);

To run this modified script and pass it an argument, enter the command:

node hello.js "John"

This should output "Hello, John!" to your terminal.

  1. Using third-party libraries in Javascript scripts
    Javascript has a large ecosystem of third-party libraries that can be used in your scripts. To use these libraries, you will need to install them using Node.js's package manager, npm.

For example, let's install the "axios" library, which is a popular library for making HTTP requests:

npm install axios

After installing the library, you can use it in your script by importing it:

const axios = require('axios');

axios.get('https://jsonplaceholder.typicode.com/posts/1')
  .then(response => {
    console.log(response.data);
  })
  .catch(error => {
    console.log(error);
  });

This script uses the axios library to make a GET request to a public API and log the response data to the terminal.

  1. Writing scripts with external dependencies
    If you are writing scripts that depend on external libraries or modules, it is recommended to use a package.json file to manage your dependencies.

To create a package.json file, navigate to your project directory in terminal and enter the command:

npm init

This will prompt you with a series of questions to configure your project, including its name, version, description, and author. It will also create a package.json file in your project directory.

To install dependencies for your project, use the command:

npm install dependency-name

For example, to install the "lodash" library, enter the command:

npm install lodash

To use this library in your script, import it using "require":

const _ = require('lodash');

const numbers = [1, 2, 3, 4, 5];
const squaredNumbers = _.map(numbers, n => n * n);
console.log(squaredNumbers);

This script uses the lodash library to square each number in an array and log the squared numbers to the terminal.

In conclusion, running Javascript scripts in terminal can be a useful tool for automating tasks or testing code snippets. With Node.js and npm, you can use third-party libraries and manage project dependencies. By following the examples in this article, you should now be able to write and run your own Javascript scripts in terminal.

  1. Installing Node.js:
    Node.js is an open-source, cross-platform runtime environment for executing Javascript code outside of the browser. It uses an event-driven, non-blocking Input/Output model that makes it lightweight and efficient. To install Node.js, you need to download the installer from the official website and follow the instructions:
  • Go to the Node.js website and download the installer for your operating system.
  • Run the installer and follow the prompts to install Node.js.
  • Verify the installation by opening the terminal and typing node -v to check the current version of Node.js installed on your system.
  1. Running Javascript files in terminal:
    You can create a .js file and run it in your terminal. For example, create a file called 'example.js' with the following code:
const name = 'John';
console.log(`Hello, ${name}!`);

Save the file, navigate to its directory in your terminal and type node example.js. The output should be Hello, John! in your terminal.

  1. Passing arguments to Javascript scripts:
    You can pass arguments to your Javascript scripts when running them in the terminal. To access these arguments, you can use the process.argv array. For example, modify the 'example.js' file to take an argument for the name:
const name = process.argv[2];
console.log(`Hello, ${name}!`);

Save the file, navigate to its directory in your terminal and type node example.js Mark. The output should be Hello, Mark! in your terminal.

  1. Using third-party libraries in Javascript scripts:
    You can use third-party libraries in your Javascript scripts by installing them with Node.js's package manager, npm, using the command npm install <library-name>. For example, install the 'moment.js' library with the command npm i moment, then use it in the following example:
const moment = require('moment');

console.log(`Today is ${moment().format('dddd, MMMM Do YYYY')}`);

This script uses moment.js to format the current date in a readable way. Moment.js is a popular library that simplifies working with dates and times in Javascript.

  1. Writing scripts with external dependencies:
    When writing Javascript scripts with external dependencies, it is recommended to use a package.json file to manage your dependencies. To create a package.json file in your project directory, run the command npm init, then follow the prompts to answer some basic questions about your project, including its name, version, description, and author.

After the package.json file has been created, you can add dependencies to your project with the command npm install <dependency-name>. For example, to install the 'request' library, type npm install request in your terminal. Then, in your script, require the library by adding the line const request = require('request').

In conclusion, running Javascript in terminal can be a powerful tool when you need to automate tasks, process data or test code snippets. By following the steps outlined in this article, you can easily install Node.js, run Javascript files or scripts with arguments, use third-party libraries and manage project dependencies with npm and a package.json file. With this knowledge, you should be able to write and run your own command-line Javascript applications with ease.

Popular questions

  1. What is Node.js and why is it needed to run Javascript in terminal?
  • Node.js is an open-source, cross-platform runtime environment for executing Javascript code outside of the browser. It is needed to run Javascript in terminal because it provides the necessary tools and libraries to execute Javascript code in a server-side environment.
  1. How do you run a Javascript file in terminal?
  • To run a Javascript file in terminal, navigate to the directory where the file is stored and type node <filename.js>.
  1. How do you pass arguments to a Javascript script when running in terminal?
  • To pass arguments to a Javascript script when running in terminal, add them after the filename, separated by spaces. Then, in your script, access them using the process.argv array.
  1. How do you install third-party libraries to use in a Javascript script?
  • Third-party libraries can be installed using Node.js's package manager, npm, with the command npm install <library-name>.
  1. What is a package.json file and why is it useful when working with Node.js and Javascript?
  • A package.json file is a metadata file that lists the dependencies and other essential information about a Node.js project. It helps manage dependencies, versions, project configuration, and scripting. When working with Node.js and Javascript, a package.json file is useful for ensuring that the project has all the necessary libraries and versions for it to run correctly.

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Jsterm

Have an amazing zeal to explore, try and learn everything that comes in way. Plan to do something big one day! TECHNICAL skills Languages - Core Java, spring, spring boot, jsf, javascript, jquery Platforms - Windows XP/7/8 , Netbeams , Xilinx's simulator Other - Basic’s of PCB wizard
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