tootlab-mastodon/app/javascript/core/settings.js

//  This file will be loaded on settings pages, regardless of theme.

const { length } = require('stringz');
const { delegate } = require('rails-ujs');

delegate(document, '#account_display_name', 'input', ({ target }) => {
  const nameCounter = document.querySelector('.name-counter');
  const name        = document.querySelector('.card .display-name strong');

  if (nameCounter) {
    nameCounter.textContent = 30 - length(target.value);
  }

  if (name) {
    name.innerHTML = emojify(target.value);
  }
});

delegate(document, '#account_note', 'input', ({ target }) => {
  const noteCounter = document.querySelector('.note-counter');

  if (noteCounter) {
    noteCounter.textContent = 160 - length(target.value);
  }
});

delegate(document, '#account_avatar', 'change', ({ target }) => {
  const avatar = document.querySelector('.card .avatar img');
  const [file] = target.files || [];
  const url = file ? URL.createObjectURL(file) : avatar.dataset.originalSrc;

  avatar.src = url;
});

delegate(document, '#account_header', 'change', ({ target }) => {
  const header = document.querySelector('.card .card__img img');
  const [file] = target.files || [];
  const url = file ? URL.createObjectURL(file) : header.dataset.originalSrc;

  header.src = url;
});

delegate(document, '#account_locked', 'change', ({ target }) => {
  const lock = document.querySelector('.card .display-name i');

  if (target.checked) {
    lock.style.display = 'inline';
  } else {
    lock.style.display = 'none';
  }
});