js实现的textarea自动变色光标特效

使用方法

const textarea = document.getElementById('comment');
const changeCursor = e => {
  let { value } = e.target;
  let newClass = getRangeColor(e.target.maxLength, value.length);

  e.target.classList.remove('good', 'warning', 'danger');
  e.target.classList.add(newClass);
};

const getRangeColor = (maxLen, inputLen) => {
  let range = maxLen / 3;

  if (between(inputLen, 0, range)) {
    return 'good';
  } else if (between(inputLen, range, range * 2)) {
    return 'warning';
  } else {
    return 'danger';
  }
};

const between = (x, min, max) => {
  return x >= min && x <= max;
};

textarea.addEventListener('input', changeCursor);