JSFiddle - React, Tailwind, and code Playground

HTML

<div class="col-md-9 col-md-offset-3 reg-login-line">
  <i class="baseline"></i>
  <div class="onoff">
    <input type="checkbox" autocomplete="off" id="register_account" name="register_account" checked="checked" value="1" onclick="return Onepage.showFields( this.checked, new Array('opc_password', 'opc_password2') );">
    <label for="register_account"></label>
  </div>

  <label for="register_account" class="as-text">Зарегистрироваться</label>
</div>

CSS

* {
  box-sizing: border-box;
}

.onoff {
  -webkit-user-select: none;
  -moz-user-select: none;
  -ms-user-select: none;
  display: inline-block;
  width: auto;
  margin: 0 0.3em 0 0;
  padding: 0;
}

.onoff input {
  display: none;
}

.onoff label {
  overflow: hidden;
  cursor: pointer;
  height: 24px;
  padding: 0;
  line-height: 20px;
  border: 1px solid #ddd;
  border-radius: 20px;
  background-color: #FFFFFF;
  transition: background-color 0.25s ease;
  margin: 0;
  width: 37px;
  position: relative;
  display: inline-block;
}

.onoff label:before {
  content: "";
  display: block;
  width: 20px;
  height: 20px;
  margin: 0px;
  background: #FFFFFF;
  position: absolute;
  top: 1px;
  bottom: 0;
  right: 14px;
  border: 0;
  -webkit-border-radius: 20px;
  -moz-border-radius: 20px;
  border-radius: 20px;
  transition: right 0.25s ease;
  -webkit-box-shadow: 0 2px 3px 0px rgba(0, 0, 0, 0.3);
  -moz-box-shadow: 0 2px 3px 0px rgba(0, 0, 0, 0.3);
  box-shadow: 0 2px 3px 0px rgba(0, 0, 0, 0.3);
}

.onoff input:checked + label {
  background-color: #49E845;
}

.onoff input:checked + label:before {
  right: 1px;
}

.baseline {
  display: inline-block;
  width: 100%;
  height: 0;
  margin-right: -100%;
  border-bottom: 1px solid rgba(65, 105, 225, .5);
}