链接地址：https://dev.w3.org/html5/html-author/charref
可以看到各个符号的不同表达方式：
注：000可以忽略不计
例：
| & | & & |
& |
& |
| " | " " |
" |
" |
| ' | ' |
' |
' |
| < | < < |
< |
< |
| = | = |
= |
= |
| > | > > |
> |
> |
| / | / |
/ |
/ |
| @ | @ |
@ |
@ |
| \ | \ |
\ |
\ |
| [ | [ [ |
| ] | ] ] |
] |
] |
| ^ | ^ |
^ |
^ |
| ; | ; |
; |
; |
| { | { { |
| } | } } |
| | | | | | |
| |
| |