ES2015-set.js - https://www.leeboonstra.com/developer/sencha-ecmascript-2015/

ES2015-set.js

var settingsset = new Set([
  [ 1, 'email'],
  [ 2, 'url']
]);

settingsset.forEach(function (value, key) {
  console.log(`Key: ${key} has value: ${value}`);
  //Key: 1,email has value: 1,email
  //Key: 2,url has value: 2,url
});

settingsset.size; //2
settingsset.add('username'); //Set [ Array[2], Array[2], "username" ]
settingsset.add({ devmode: true }); //Set [ Array[2], Array[2], "username", Object ]

settingsset.has('username'); //true
settingsset.delete('username'); //true
settingsset.has('username'); //false
console.log(settingsset); //Set [ Array[2], Array[2], Object ]

settingsset.clear(); 
settingsset.size; //0