JSFiddle - React, Tailwind, and code Playground

HTML

<div user_id="u1" day_status="1" day="d1" class="day"></div>
<div user_id="u1" day_status="1" day="d2" class="day"></div>
<div user_id="u1" day_status="0" day="d3" class="day"></div>
<div user_id="u2" day_status="1" day="d4" class="day"></div>
<div user_id="u2" day_status="1" day="d5" class="day"></div>
<div user_id="u2" day_status="1" day="d6" class="day"></div>
<div user_id="u2" day_status="0" day="d7" class="day"></div>
<div user_id="u2" day_status="0" day="d8" class="day"></div>

JavaScript

function es_parse_workingSheduler_data(){
  const data = {};

  document.querySelectorAll('.day[user_id]')
    .forEach(elem => {
    const userId = elem.getAttribute('user_id');
    const status = elem.getAttribute('day_status');
    const day = elem.getAttribute('day');
    if (status.length) {
      data[userId] = data[userId] || {};
      data[userId][day] = status;
    }
  });

  console.log(data);
  return data;
}

es_parse_workingSheduler_data();