Pass an object of key: value pairs to be uri encoded (does prepend the '?')

encodeQueryData.js

// es5
function encodeQueryData(data) {
  return '?' + Object.keys(data).map(function(key) {
    return [key, data[key]].map(encodeURIComponent).join("=");
  }).join("&");
}

// es6
const encodeQueryData = data => '?' + Object.keys(data).map(key => [key, data[key]].map(encodeURIComponent).join("=")).join('&');