1、给required设置提示信息
<input class="is_required form-control"
type="text"
id="product_name"
name="product_name"
value=""
placeholder="Apply Product Name"
required
oninvalid="setCustomValidity('This item is a required item.');"
oninput="setCustomValidity('');" />
2、给特定的条件设置提示信息
<input class="is_required form-control"
type="text"
id="share_link_1"
name="share_link_1"
value=""
placeholder="Share Link:"
pattern="[a-zA-z]+://[^\s]*"
oninvalid="setCustomValidity('请输入url');"
oninput="setCustomValidity('');" />