表单SELECT 使用 CSS 设置下拉箭头样式-生于七零年代

今天碰到一个需求，要到表单中的select的下拉箭头做美化。在网上搜索了一下，大部分是用图片来实现的，这个项目主要是手机端微信扫码，用微信内置浏览器访问，所以还是全部用CSS来实现比较好。下面是样例：

HTML代码

<h1>SELECT 使用 CSS 来设置箭头。</h1>

<select class="classic">
  <option>CSS SELECT 箭头</option>
  <option>不使用图片</option>
  <option>选项</option>
</select>
<br><br>
<select class="round">
  <option>CSS SELECT 箭头</option>
  <option>不使用图片</option>
  <option>选项</option>
</select>
<br><br>
<select class="minimal">
  <option>CSS SELECT 箭头</option>
  <option>不使用图片</option>
  <option>选项</option>
</select>

CSS代码

select {

  /* styling */
  background-color: white;
  border: thin solid blue;
  border-radius: 4px;
  display: inline-block;
  font: inherit;
  line-height: 1.5em;
  padding: 0.5em 3.5em 0.5em 1em;

  /* reset */

  margin: 0;      
  -webkit-box-sizing: border-box;
  -moz-box-sizing: border-box;
  box-sizing: border-box;
  -webkit-appearance: none;
  -moz-appearance: none;
}

/* arrows */

select.classic {
  background-image:
    linear-gradient(45deg, transparent 50%, blue 50%),
    linear-gradient(135deg, blue 50%, transparent 50%),
    linear-gradient(to right, skyblue, skyblue);
  background-position:
    calc(100% - 20px) calc(1em + 2px),
    calc(100% - 15px) calc(1em + 2px),
    100% 0;
  background-size:
    5px 5px,
    5px 5px,
    2.5em 2.5em;
  background-repeat: no-repeat;
}

select.classic:focus {
  background-image:
    linear-gradient(45deg, white 50%, transparent 50%),
    linear-gradient(135deg, transparent 50%, white 50%),
    linear-gradient(to right, gray, gray);
  background-position:
    calc(100% - 15px) 1em,
    calc(100% - 20px) 1em,
    100% 0;
  background-size:
    5px 5px,
    5px 5px,
    2.5em 2.5em;
  background-repeat: no-repeat;
  border-color: grey;
  outline: 0;
}

select.round {
  background-image:
    linear-gradient(45deg, transparent 50%, gray 50%),
    linear-gradient(135deg, gray 50%, transparent 50%),
    radial-gradient(#ddd 70%, transparent 72%);
  background-position:
    calc(100% - 20px) calc(1em + 2px),
    calc(100% - 15px) calc(1em + 2px),
    calc(100% - .5em) .5em;
  background-size:
    5px 5px,
    5px 5px,
    1.5em 1.5em;
  background-repeat: no-repeat;
}

select.round:focus {
  background-image:
    linear-gradient(45deg, white 50%, transparent 50%),
    linear-gradient(135deg, transparent 50%, white 50%),
    radial-gradient(gray 70%, transparent 72%);
  background-position:
    calc(100% - 15px) 1em,
    calc(100% - 20px) 1em,
    calc(100% - .5em) .5em;
  background-size:
    5px 5px,
    5px 5px,
    1.5em 1.5em;
  background-repeat: no-repeat;
  border-color: green;
  outline: 0;
}

select.minimal {
  background-image:
    linear-gradient(45deg, transparent 50%, gray 50%),
    linear-gradient(135deg, gray 50%, transparent 50%),
    linear-gradient(to right, #ccc, #ccc);
  background-position:
    calc(100% - 20px) calc(1em + 2px),
    calc(100% - 15px) calc(1em + 2px),
    calc(100% - 2.5em) 0.5em;
  background-size:
    5px 5px,
    5px 5px,
    1px 1.5em;
  background-repeat: no-repeat;
}

select.minimal:focus {
  background-image:
    linear-gradient(45deg, green 50%, transparent 50%),
    linear-gradient(135deg, transparent 50%, green 50%),
    linear-gradient(to right, #ccc, #ccc);
  background-position:
    calc(100% - 15px) 1em,
    calc(100% - 20px) 1em,
    calc(100% - 2.5em) 0.5em;
  background-size:
    5px 5px,
    5px 5px,
    1px 1.5em;
  background-repeat: no-repeat;
  border-color: green;
  outline: 0;
}

select:-moz-focusring {
  color: transparent;
  text-shadow: 0 0 0 #000;
}

body {
  background-color: rgb(0,159,214);
  font: bold 1em/100% "Helvetica Neue", Arial, sans-serif;
  padding: 2em 0;
  text-align: center;
}
h1 {
  color: white;
  line-height: 120%;
  margin: 0 auto 2rem auto;
  max-width: 30rem;
}