I'm looking for some ways to optimize my projects, both in performance and in practicality and speed, and I came across the following question, what is the most appropriate way to delegate some values ​​without losing too much performance? using function? objects?

e.g:

Objects

var z = {
  fec: 'firstElementChild',
  nx: 'nextElementSibling',
  pr: 'previuousElementSibling',
  cl: 'className',
  ci: 'clientInformation',
  qs: 'querySelector',
  qsa: 'querySelectorAll'
}

document[z.qs]('h3');

Functions

function qs(el) {
  return document.querySelector(el);
}
qs('p');