https://developer.mozilla.org/zh-CN/docs/Web/HTML/Element/Input
<input type="number" maxlength="3" size="12" placeholder="number" />
<input type="text" maxlength="3" size="12" placeholder="text" />
maxlength="3", size="12" 对 type="number" 不生效!
https://developer.mozilla.org/zh-CN/docs/Web/HTML/Element/Input
<input type="number" maxlength="3" size="12" placeholder="number" />
<input type="text" maxlength="3" size="12" placeholder="text" />
maxlength="3", size="12" 对 type="number" 不生效!
js-get-html5-input-value