[Tools] Create a Simple CLI Tool in Node.js with CAC

Command-line tools can help you with all sorts of tasks. This lesson covers the very basics of setting up a CLI tool in Node.js by creating your project with npm, setting up your bin script, and using CAC to parse a single argument.

Create a new project, change the "name" porp's value to "hi", then add a "bin" prop, so next time, when we invoke "hi", it will run the command in "bin".

package.json

{
  "name": "hi",
  "version": "1.0.0",
  "description": "",
  "main": "index.js",
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1"
  },
  "keywords": [],
  "author": "",
  "license": "ISC",
  "bin": "./index.js",
  "devDependencies": {
    "cac": "6.3.12"
  }
}

Install:

npm i -D cac

Create index.js file:

Make sure you have '
```
#!/usr/bin/env node
```
' on the top of the file, then it knows should run in node env.
Using cac to build commad, you can define 'option', 'command'
Last you should always call cli.parse() to run the command

#!/usr/bin/env node

const cli = require('cac')();
cli.option('--type <type>', 'Provide type, [date|foo]')
// name is a required field
cli.command('<name>', 'Provide your name')
    .action((name, options) => {
        const {type} = options;
        if (type === 'date') {
            console.log(`Hi ${name}, Today is ${new Date().toDateString()}`)
        } else if (type === 'foo') {
            console.log(`Hi ${name}, you should take a rest!`)
        } else {
            console.log(`Hi ${name}, Good job!`)
        }
        
    })

cli.help()
// Display version number when `-h` or `--help` appears
cli.version('0.0.0')
cli.parse()