1、keydown()
keydown事件会在键盘按下时触发.
2、keyup()
keyup事件会在按键释放时触发,也就是你按下键盘起来后的事件
3、keypress()
keypress事件会在敲击按键时触发,我们可以理解为按下并抬起同一个按键
对应值：
keycode 8 = BackSpace BackSpace
keycode 9 = Tab Tab
keycode12 = Clear
keycode13 = Enter
keycode16 = Shift_L
keycode17 = Control_L
keycode18 = Alt_L
keycode19 = Pause
keycode20 = Caps_Lock
keycode27 = Escape Escape
keycode32 = space space
keycode33 = Prior
keycode34 = Next
keycode35 = End
keycode36 = Home
keycode37 = Left
keycode38 = Up
keycode39 = Right
keycode40 = Down
keycode41 = Select
keycode42 = Print
keycode43 = Execute
keycode45 = Insert
keycode46 = Delete
keycode47 = Help
keycode48 = 0 equal braceright
keycode49 = 1 exclam onesuperior
keycode50 = 2 quotedbl twosuperior
keycode51 = 3 section threesuperior
keycode52 = 4 dollar
keycode53 = 5 percent
keycode54 = 6 ampersand
keycode55 = 7 slash braceleft
keycode56 = 8 parenleft bracketleft
keycode57 = 9 parenright bracketright
keycode65 = a A
keycode66 = b B
keycode67 = c C
keycode68 = d D
keycode69 = e E EuroSign
keycode70 = f F
keycode71 = g G
keycode72 = h H
keycode73 = i I
keycode74 = j J
keycode75 = k K
keycode76 = l L
keycode77 = m M mu
keycode78 = n N
keycode79 = o O
keycode80 = p P
keycode81 = q Q at
keycode82 = r R
keycode83 = s S
keycode84 = t T
keycode85 = u U
keycode86 = v V
keycode87 = w W
keycode88 = x X
keycode89 = y Y
keycode90 = z Z
keycode96 = KP_0 KP_0
keycode97 = KP_1 KP_1
keycode98 = KP_2 KP_2
keycode99 = KP_3 KP_3
keycode 100 = KP_4 KP_4
keycode 101 = KP_5 KP_5
keycode 102 = KP_6 KP_6
keycode 103 = KP_7 KP_7
keycode 104 = KP_8 KP_8
keycode 105 = KP_9 KP_9
keycode 106 = KP_Multiply KP_Multiply
keycode 107 = KP_Add KP_Add
keycode 108 = KP_Separator KP_Separator
keycode 109 = KP_Subtract KP_Subtract
keycode 110 = KP_Decimal KP_Decimal
keycode 111 = KP_Divide KP_Divide
keycode 112 = F1
keycode 113 = F2
keycode 114 = F3
keycode 115 = F4
keycode 116 = F5
keycode 117 = F6
keycode 118 = F7
keycode 119 = F8
keycode 120 = F9
keycode 121 = F10
keycode 122 = F11
keycode 123 = F12
keycode 124 = F13
keycode 125 = F14
keycode 126 = F15
keycode 127 = F16
keycode 128 = F17
keycode 129 = F18
keycode 130 = F19
keycode 131 = F20
keycode 132 = F21
keycode 133 = F22
keycode 134 = F23
keycode 135 = F24
keycode 136 = Num_Lock
keycode 137 = Scroll_Lock
keycode 187 = acute grave
keycode 188 = comma semicolon
keycode 189 = minus underscore
keycode 190 = period colon
keycode 192 = numbersign apostrophe
keycode 210 = plusminus hyphen macron
keycode 211 =
keycode 212 = copyright registered
keycode 213 = guillemotleft guillemotright
keycode 214 = masculine ordfeminine
keycode 215 = ae AE
keycode 216 = cent yen
keycode 217 = questiondown exclamdown
keycode 218 = onequarter onehalf threequarters
keycode 220 = less greater bar
keycode 221 = plus asterisk asciitilde
keycode 227 = multiply division
keycode 228 = acircumflex Acircumflex
keycode 229 = ecircumflex Ecircumflex
keycode 230 = icircumflex Icircumflex
keycode 231 = ocircumflex Ocircumflex
keycode 232 = ucircumflex Ucircumflex
keycode 233 = ntilde Ntilde
keycode 234 = yacute Yacute
keycode 235 = oslash Ooblique
keycode 236 = aring Aring
keycode 237 = ccedilla Ccedilla
keycode 238 = thorn THORN
keycode 239 = eth ETH
keycode 240 = diaeresis cedilla currency
keycode 241 = agrave Agrave atilde Atilde
keycode 242 = egrave Egrave
keycode 243 = igrave Igrave
keycode 244 = ograve Ograve otilde Otilde
keycode 245 = ugrave Ugrave
keycode 246 = adiaeresis Adiaeresis
keycode 247 = ediaeresis Ediaeresis
keycode 248 = idiaeresis Idiaeresis
keycode 249 = odiaeresis Odiaeresis
keycode 250 = udiaeresis Udiaeresis
keycode 251 = ssharp question backslash
keycode 252 = asciicircum degree
keycode 253 = 3 sterling
keycode 254 = Mode_switch
iphoneX 微信页面下 拉起键盘后关闭键盘，原键盘区域还存在
js 没有办法对手机软键盘直接进行监听的
那是否可以对 input 失去焦点进行监听
搜一了一个 MDN Web 文档 ，发现
focus 和 blur 不会冒泡，而 focusin 和 focusout 可以支持冒泡，加事件代理，当触发 focusout 事件后滚一下
测试后发现 ios 可以监听到 focusout 事件，而 android 在键盘收起后，input 仍处于焦点状态，无法触发 focusout 事件
添加 resize 事件后 发现 android 在唤起键盘收起键盘后 window.innerHeight 会有改变，而 ios 不会
js 移动端对键盘监听
原生键盘监听事件：按下一次按键，分为三个过程，按下—按住—松开onkeydown：某个键被按下
onkeypress：某个键盘的键被按下或按住
onkeyup：某个键盘的键被松开
使用方法，一般来说，键盘监听是直接在整个页面文档上进行监听的，也就是document上
以下是原生的使用案例
//实际使用
document.onkeydown=function(e){ //对整个页面文档监听
var keyNum=window.event ? e.keyCode :e.which //获取被按下的键值
//判断如果用户按下了回车键（keycody=13）
if(keyNum==13){
alert('您按下了回车')
}
//判断如果用户按下了空格键(keycode=32)，
if(keyNum==32){
alert('您按下了空格')
}
}
剩下另外两个按键方法同理
jquery的方式监听键盘事件
jquery的也分为三个过程，但是在事件名称上有所不同
keyup：某个键盘的键被松开
keydown：某个键被按下
keypress：某个键盘的键被按下或按住
