username_checker = el => {
  let element = new d(el)
  let uc = new d('.username_checker')

  element.on('keyup', async e => {
    let value = e.target.value
    uc.show()

    if (value) {
      let { data: count } = await post('/user/username-checker', { value })
      let html

      if (count == 0) {
        html =
          '<span class="checker_text">username is available</span><span class="checker_icon"><i class="far fa-smile"></i></span>'

        uc.mutipleCSS({
          width: '160px',
          right: '-188px',
        })
      } else {
        html =
          '<span class="checker_text">username already taken</span><span class="checker_icon"><i class="far fa-frown"></i></span>'

        uc.mutipleCSS({
          width: '167px',
          right: '-194px',
        })
      }

      uc.html(html)
    } else {
      uc.hide()
    }
  })

  element.on('blur', () => uc.hide())
}
For username checker
@param {String} el