urlBuilder.js

const buildUrl = function(url, params) {
  let _url = url
  if (url.indexOf('?') === -1) {
    _url = url + '?'
  }
  
  let queries = []
  
  Object.keys(params).forEach(function(key) {
    queries.push(`${key}=${params[key]}`)
  })
  
  return _url + queries.join('&')
}

console.log(buildUrl('/booking' ,{ foo: 'bar', bar: 'baz' })) // returns /booking?foo=bar&bar=baz