Node.js yargs package

المعرفة:: NodeJS
الحالة:: ملاحظة_مؤرشفة
المراجع:: The Complete Node.js Developer Course 3rd Edition, coggro’s Notes

Introduction¶

• Node.js provides a bare-bones way to access command line arguments. While it’s a good start, it doesn’t provide any way to parse more complex command line arguments.
• Yargs helps you build interactive command line tools, by parsing arguments and generating an elegant user interface.
• https://www.npmjs.com/package/yargs

Installing and Setting Up Yargs¶

npm install yargs@12.0.2  

• yargs can be used to make it easier to work with command line arguments. The example below shows how this can be done. First, yargs.version is used to set up a version for the command line tool. Next, yargs.command is used to add support for a new command.

const yargs = require('yargs')  

// Customize version  
yargs.version('1.1.0')  

// Add command  
yargs.command({  
    command: 'add',  
    describe: 'Add a new note',  
    handler: function () {  
        console.log('Adding a new note!')  
    }  
})  

console.log(yargs.argv)  

• This command can be triggered by providing its name as a command line argument.

$ node app.js add  
# Adding a new note!  

• Yargs provides a many useful commands by default, such as tool’s version and auto-generated documentation that explains how the tool can be used.

$ node app.js --version  
# 1.1.0  

$ node app.js --help  

• Yargs exposes a much more reasonable object of arguments: node app.js add --title="things to buy" yields { _: [ 'add' ], title: 'things to buy', '$0': 'app.js' }.
• We can set up commands using .command({command object}) function.

args  
  .command({  
    command: `add`,  
    description: `Add a new note`,  
    handler: () => {  
      console.log(`Adding a new note.`)  
    },  
  })  
  .command({  
    command: `remove`,  
    description: `Remove a note.`,  
    handler: () => {  
      console.log(`Removing a note.`)  
    },  
  })  

Adding Command Options¶

• Options are additional pieces of information passed along with the command. You can set up options for a command using the builder property as shown below.
• The add command can be used with two options. The first is title which is used for the title of the note being added. The second is body which is used for the body of the note being added. Both options are required because demandOption is set to true. Both are also set up to accept string input because type is set to ‘string’.

yargs.command({  
  command: `add`,  
  description: `Add a new note`,  
  builder: {  
    title: {  
      describe: `Note title`, // Describe option for help  
      demandOption: true, // Require option  
      type: `string`, // Force a string value  
    },  
  },  
  // Add argv to arguments here and use in funcution  
  handler: (argv) => {  
    console.log(`Title: ${argv.title}`)  
  },  
})  

$ node app.js add --title="Buy" --body="Note body here"  
Title: Buy  
Body: Note body here  

• Accessing argv from the actual args object forces it to actually parse. console.log(args.argv). However, we can force a parse without logging by using args.parse().

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