<!DOCTYPE html>action="form-action.php"搜索: type="search" id="mySearch" name="filter"type="submit" value="提交"点击 "点我" 按钮设置搜索字段 required 属性。提示: 在点击 “点我” 按钮前后点击 "提交" 按钮查看效果onclick="myFunction()"点我id="demo"function myFunction() {document.getElementById("mySearch").required = true;document.getElementById("demo").innerHTML = " required 属性已设置。表单提交前搜索字段为必填字段。 ";}