omit "One"-liner

omit.js

const omit = (obj, omitProps) => Object.keys(obj)
  .filter(key => omitProps.indexOf(key)===-1)
  .reduce((returnObj, key) => ({ ...returnObj, [key]: obj[key] }), {})

usage.js

const myObject = {a:'1', b:'2', c:'3', d:'4'}

omit(myObject, ['a','c'])
// Object {b: "2", d: "4"}

omit(myObject, ['a'])
// Object {b: "2", c: "3", d: "4"}