Examples of Yargs Module in Node Js - Node Js Tutorial

After writing article about Creating Simple CRUD Using Node js, Express, Mongodb and Bootstrap For Beginner and Using fs (File System) Module in Node js to Write and Read File - Node Js Tutorial , now in this article I am going to share about the use of Yargs. Just heard about yargs ?. Me too.

Node Js Tutorial - Examples of Yargs Module in Node Js

yargs is one of the famous javascript module. Yargs helps us build interactive command line tools, by parsing arguments and generating an elegant user interface.

Ok so, let's try together what can we do with this nodejs module, Yargs.

install yargs

npm install yargs

make a folder containing 2 files

yargs files

yargs.js file - Node Js Tutorial - Yargs Examples

yargs.js contains yargs command. Later we will run this file.

const yargs = require('yargs')
const note = require('./yargfunction')

//EXAMPLE TO WRITE 
yargs.command({
    command: 'add', // set the command
    describe: 'to add data', //give description
    builder: { //set the builder -- it contains the key to sore the value
        title: {
            demandOption: true, //required?
            type: 'string',
            describe: 'this is the title'
        },
        content: {
            type: 'string',
            demandOption: true,
            describe: 'this is the content'

        }
    },
    handler: function (argv) { //handler is the place we can put function
        console.log(`title: ${argv.title}, conten: ${argv.content}`)
    }
})

//EXAMPLE 2 - TO WRITE
yargs.command({
    command: 'mymessage',
    describe: 'maybe you need to say hello first',
    builder: {
        message: {
            type: 'string',
            demandOption: 'required'
        }
    },
    handler: function (argv) {
        if (argv.message == "hello") {
            console.log(`oh you say ${argv.message} ? hiiiii :*`)
        } else {
            console.log(`why you don't say hello first ??`)

        }
    }

})

// EXAMPLE 3 CREATE and UPDATE JSON FILE USING FS and Yargs
yargs.command({
    command: 'addJSONFile',
    describe: 'function to add json file',
    builder: {
        title: {
            type: 'string',
            describe: 'this is the title'
        },
        content: {
            type: 'string',
            describe: 'this is the content'
        }
    },
    handler: function (argv) {
        //call function from yargfunction.js
        note.addNote(argv.title, argv.content)
    }
})

//Update JSON
yargs.command({
    command: 'updateJSONFile',
    describe: 'this is to update existing json file',
    builder: {
        thefilename: {
            type: 'string',
            demandOption: true,
            describe: 'this is the filename'
        },
        updatedTitle: {
            type: 'string',
            demandOption: true,
            describe: 'this is the titile'
        },
        updatedContent: {
            type: 'string',
            demandOption: true,
            describe: "this is the content content"
        }
    },
    handler: function (argv) {
        //The name of the variable argv stands for "argument vector". A vector is a one-dimensional array, and argv is a one-dimensional array of strings. Each string is one of the arguments that was passed to the program. source: crasseux.com
        //call function from yargfunction.js
        note.updateNote(argv.thefilename, argv.updatedTitle, argv.updatedContent)
    }
})

yargs.parse() // to parse the result

yargfunction.js file - Node Js Tutorial - Yargs Examples

yargfunction.js is the file containing functions that are needed to run one command in yargs,js file.

const fs = require('fs')

//addnote function
const addNote = function (title, content) { //set the parameter
    const rawData = {
        title: title,
        content: content
    }
    const toJsonstring = JSON.stringify(rawData) //make the objevt becomes json form in string
    fs.writeFileSync('yarg.json', toJsonstring) //use fs function to create a file and insert data (toJsonString variable)
}

//update function
const updateNote = function (thefilename, title, content) {
    const readFileBuffer = fs.readFileSync(`${thefilename}`) //read the file
    const stringIt = readFileBuffer.toString() // change the readFileBuffer to string, because the result of readFileBuffer is in binary
    console.log(stringIt)

    const makeItJsonObject = JSON.parse(stringIt) //convert the json string to object, so we will be able to modify the value
    console.log(makeItJsonObject)

    //set the change
    makeItJsonObject.title = title
    makeItJsonObject.content = content
    console.log(makeItJsonObject)

    const stringitagain = JSON.stringify(makeItJsonObject) //after changing the value, then we can convert it again to json string
    console.log(stringitagain)

    fs.writeFileSync(`${thefilename}`, stringitagain) // and finally we can rewrite the file with the new data
}

module.exports = { addNote, updateNote }

Simple example

1. Make simple note

in this first example we are going to create yargs command to record our input through console. 

how to run it?

open console and run :

node yarg.js add --title="YOUR_TITLE" --content="YOUR_CONTENT"

if we run that command the result will be shown in the console

FIrst example of yargs - Examples of Yargs Module in Node Js - Node Js Tutorial

2.Combining yargs with else if condition

in this example I am going to use yargs to return values regarding the input.

how to run it
open console and run:

node yarg.js mymessage --message="easy ?"

The result will be like this

second example of yargs - Examples of Yargs Module in Node Js - Node Js Tutorial

3. Creating Json file using yargs and update it

first we will add a json file and write a json value. you can write the code like below

third example of yargs - Examples of Yargs Module in Node Js - Node Js Tutorial

then, we can see that the json file is already created and inside the file there are some lines of code of json. yarg.json is resulted from the yargfunction.js.

yarg.json - Examples of Yargs Module in Node Js - Node Js Tutorial

if we want to update it, we can use this command (like beow image)

update commnd yargs - Examples of Yargs Module in Node Js - Node Js Tutorial

then if we see the json file, it will change automatically.

yarg.json - Examples of Yargs Module in Node Js - Node Js Tutorial

I hope it can be useful. You can check about this simple project in my github : https://github.com/ZenHuzaini/nodejs-yargs-examples

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Author : zenhuzaini

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