otp.js

const http = require('http');

function sendOTP (phone, callback) => {
  let path = '/api/sendotp.php?otp_length=6&authkey=' + OTP_AUTH_KEY +
    '&message=&sender=MySHIK&mobile=+91'+ phone +'&otp_expiry=5';

  path = encodeURI(path);
  let options = {
    'method': 'POST',
    'hostname': 'control.msg91.com',
    'port': null,
    'path': path,
    'headers': {},
  };

  let req = http.request(options, function(res) {
    let chunks = [];

    res.on('data', function(chunk) {
      chunks.push(chunk);
    });

    res.on('end', function() {
      let body = Buffer.concat(chunks);
      try {
        callback(null, JSON.parse(body.toString()));
      } catch (err) {
        callback('Some error occurred');
      }
    });
  });

  req.end();
};