how do I clone a git repository using node.js specific commands

Well, You can use shelljs or nodegit package. Let me describe a way to use shelljs.

const shell = require('shelljs')
const path = process.cwd
shell.cd(path)
shell.exec('git clone https://github.com/<github-name>/<git-repos>')

Then it is a way to use nodegit.

const clone = require("nodegit").Clone.clone

const path = process.cwd

clone("https://github.com/<github-name>/<git-repos>", path)
  .then(function () {
    // Repo is available in `path`
  })

Adding onto @Venus713's solution, you can use node-cmd to clone repositories.

const cmd = require('node-cmd');
const clone = cmd.runSync('git clone https://github.com/<username>/<repo>');

// runSync returns the output of the command, which is console logged below.

console.log(clone);