gistfile1.txt

// https://documentation.onesignal.com/reference#create-notification
var request = require('request');
var Promise = require("bluebird");

// email, templateId are required
module.exports = async function (email, templateId, payload) {
  var message = '', heading = '', subtitle = '';
  var restKey = process.env.ONE_SIGNAL_REST_KEY;
  var appID = process.env.ONE_SIGNAL_APP_ID;

  var body = {
    'app_id': appID,
    'template_id': templateId,
    'filters': [
      {
        "field": "email",
        "value": email
      }, 
    ]
  }

  if (payload) {
    message = payload.message || message
    heading = payload.heading || heading
    subtitle = payload.subtitle || subtitle

    // Optional parameters shouldn't appear in body
    // But if provided, it cannot be empty
    body = Object.assign({}, body, {
      'contents': { en: message }, // message
      'headings': { en: heading }, // title
      'subtitle': { en: subtitle }, // subtitle
    })
  }

  return await new Promise((resolve, reject) => {
    request({
      method: 'POST',
      uri: 'https://onesignal.com/api/v1/notifications',
      headers: {
        "authorization": `Basic ${restKey}`,
        "content-type": "application/json"
      },
      json: true,
      body
    },
    function (error, response, body) {
      if (!error && !body.errors) {
        console.log(body);
        resolve(body)
      } else {
        console.error('Error:', error, body.errors);
        reject([error, body.errors])
      }
    });
  })
}