Succinct/concise syntax for ‘optional’ object keys in ES6/ES7?

let flag1 = true;
let flag2 = false;

// extra cases added by Abdull
let optionalKey8 = 8;
let optionalKey9 = undefined;
let optionalKey10 = false;
let optionalKey11 = null;
let optionalKey12 = "twelve";

const obj = { 
  requiredKey1: 1, 
  requiredKey2: 2,
  ...(flag1 && { optionalKey3: 3 }),
  ...(flag2 && { optionalKey4: 4, optionalKey5: 5 }),  // ignored
  ...(flag1 && { optionalKey6: 6, optionalKey7: 7 }),
  ...(optionalKey8 && { optionalKey8 }),
  ...(optionalKey9 && { optionalKey9 }), // ignored
  ...(optionalKey10 && { optionalKey10 }), // ignored
  ...(optionalKey11 && { optionalKey11 }), // ignored
  ...(optionalKey12 && { optionalKey12 })
};

console.log(obj);