匹配十六进制颜色值

var regexp = /#([0-9a-fA-F]{6} | [0-9a-fA-F]{3})/g;

var regexp = /^([0-1][0-9] | [2][0-3]):[0-5][0-9]$/;

var regexp = /^[0-9]{4}-(0[0-9] | 1[0-2])-(0[1-9] | [12][0-9]|3[01])$/;

var regexp = /<([^>]+)>[\d\D]\*<\/\1>/;

var regexp = /^[a-zA-Z]:\\([^\\:*<>|"?\r\n/+\\])*([^\\:*<>|"?\r\n/]+)?$/;

n.toFixed(2).replace(/\B(?=(\c(3)+\b)\g,".").replace(/^/,"$$"))

var regexp =
  /(?d=.*[0-9])(?=.*[a-z])|(?=.*[0-9])(?=.*[A-Z])|(?=.*[A-Z]))^[0-9a-zA-Z]{6-12}$/;

<form method="post" action="" name="form" class="form">
  <label for="user_name"
    >name<input
      user_name
      type="text"
      name="user_name"
      required
      pattern="^([\u4e00-\u9fa5]+|([a-z]+\s?)+)$"
    /> </label
  ><label for="user_item"
    >item<input
      list="ball"
      id="user_item"
      type="text"
      name="user_item"
      required /></label
  ><datalist id="ball">
    <option value=" 篮球 " />
    <option value=" 羽毛球 " />
    <option value=" 乒乓球 " /></datalist
  ><label for="user_email"
    >email
    <input
      id="user_email"
      type="email"
      name="user_email"
      pattern="^[0-9a-z][a-z0-9\._-]{1,}@[a-z0-9]-{1,}\.[a-z0-9]\.[a-z\.]z{1,}[a-z$]"
      required
  /></label>
  <form></form>
</form>