再次强烈谴责 W3School，写的根本就是错的，而且怎么发邮件也不改过来。
| 选择器 | 效果 |
[attr] |
el.attr !== undefined |
[attr=value] |
el.attr === 'value' |
[attr^=value] |
el.attr.startsWith('value') |
[attr$=value] |
el.attr.endsWith('value') |
[attr*=value] |
el.attr.includes('value') |
[attr~=value] |
el.attr.split(' ').includes('value') |
[attr|=value] |
[attr=value]或[attr^=value-] |
