[JAVA] Used from the introduction of Node.js in WSL environment

Introduction

It is mainly used as a memorandum for posters. Introduce Node.js, which is useful for creating the Web.

environment

Install on wsl (Windows Subsystem for Linux).

Editor: VSCode
Shell: bash version 4.4.20
Ubuntu: 18.04.4 LTS

table of contents

1. Introduction of nvm [>>](Introduction of # 1 nvm)
2. Introduction of Node.js [>>](Introduction of # 2 nodejs)
3. Try using the REPL [>>](Try using # 3 repl)
4. Try running the file [>>](4 Try running the file)

1. Introduction of nvm

First, install nvm to manage the version of Node.js. Knowing the version of Node.js you are currently using You can switch to another version.

wsl

$ curl -o- https://raw.githubusercontent.com/creationix/nvm/v0.34.0/install.sh | bash

When you're done

wsl

$ source ~/.bashrc 

Then, read the contents of .bashrc.

wsl

$ nvm

Node Version Manager

Note: <version> refers to any version-like string nvm understands. This includes:
  - full or partial version numbers, starting with an optional "v" (0.10, v0.1.2, v1)
  - default (built-in) aliases: node, stable, unstable, iojs, system
  - custom aliases you define with `nvm alias foo`
The following is omitted. .. ..

If so, the installation is successful.

2. Introduction of Node.js

This time, I installed Node.js of Ver. 10.14.2.

wsl

$ nvm install v10.14.2

Downloading and installing node v10.14.2...
Downloading https://nodejs.org/dist/v10.14.2/node-v10.14.2-linux-x64.tar.xz...
###################################################################### 100.0%Computing checksum with sha256sum
Checksums matched!
Now using node v10.14.2 (npm v6.4.1)
Creating default alias: default -> v10.14.2

$ nvm use v10.14.2
Now using node v10.14.2 (npm v6.4.1)

$ node --version
v10.14.2

I have confirmed that the specified version of Node.js is installed.

3. Try using REPL

Think of it as a Node.js version of the console. (It feels like a Python console in Python) You can exit the REPL twice with Ctrl + c.

REPL

$ node
> 1+1
2
>
(To exit, press ^C again or type .exit)
> 

4. Try running the file

I think that the way to write the program should be the same as JavaScript. This time I will write a simple addition program and run it.

Source code

sum.js

'use strict';
function aAdd(num) {
    var res = 0;
    num[0] = 0;
    num[1] = 0;
    for (let s of num) {
        res += parseInt(s);
    }
    console.log(res);
}
aAdd(process.argv);

Execution result

wsl

$ node sum.js 1 2 3 4
10
$ node sum.js      
0

Rough commentary

This was a program that summed the arguments. The instructions are listed in process.argv. If you run $ node sum.js 1 1 1 2 3 The contents of the list are

[ '/home/yosse95ai/.nvm/versions/node/v10.14.2/bin/node',
  '/home/yosse95ai/sum.js',
  '1',
  '1',
  '1',
  '2',
  '3' ]

And so on.

So

num[0] = 0;
num[1] = 0;

Replace the non-numeric character string part (path part) with 0 in the part of. I think there is probably a more clever way.

in conclusion

This time, it was a fairly rudimentary commentary. I'm still a beginner, so I wrote it to organize my mind. It was probably a poor sentence, but thank you for your relationship. Goodbye: wave:

Related article

-Used from yarn introduction for Node.js in Linux environment

reference

-N Preparatory School 2020 Introduction to Programming