hadChanged.js

const hadChanged = list => obj => Object.keys(list)
  .filter(k => obj[k] !== list[k])
  .reduce((a, b) => {
    list[b] = obj[b]
    return a || !!b
  }, false)

export default hadChanged
/*
var list = { a: 'a', b: 'b'}
var obj = { a: 'a', b: 'b', c: 'c'}

var checkAB = hadChanged(list)
checkAB(obj)
obj.c = 'defg'
checkAB(obj)
obj.a = 'u'
checkAB(obj)
checkAB(obj)
checkAB({})
checkAB({})

var checkVoid = hadChanged({})
checkVoid(obj)
checkVoid(obj)
checkVoid({})
*/