Operation of javascript keyboard up and down keys (selection)_javascript skills

Two paragraphs of code for selecting using the up and down keys of the keyboard:
First paragraph

<style> TD { cursor: hand; } </style> <table id="oTable" style="width:240px;border:1px highlight solid; font-size:12px;"> <tr> <td style="background-color:#dcdcdc;">鼠标点击或按↑↓改变行的颜色</td> </tr> <tr> <td>鼠标点击或按↑↓改变行的颜色</td> </tr> <tr> <td>鼠标点击或按↑↓改变行的颜色</td> </tr> <tr> <td>鼠标点击或按↑↓改变行的颜色</td> </tr> </table>
[Ctrl A Select all Note: If you need to introduce external Js, you need to refresh to execute

]
Second paragraph

<table id="tb"> <tr> <td>00000000000000</td> </tr> <tr> <td>11111111111111</td> </tr> <tr><td>22222222222222</td></tr> <tr><td>33333333333333</td></tr> </table> <input type="text" name="show" value="do">
[Ctrl A select all Note:

If you need to introduce external Js, you need to refresh to execute
]<script> var i=0; function document.onkeydown(){ if (event.keyCode == 38){ for(var k=0;k<document.getElementById('tb').rows.length;k++){ document.getElementById('tb').rows(k).bgColor=""; } document.getElementById('tb').rows(--i%tb.rows.length).bgColor="#FF0000"; document.all.show.value=document.getElementById('tb').rows(i%tb.rows.length).innerText; } if (event.keyCode== 40){ for(var k=0;k<document.getElementById('tb').rows.length;k++){ document.getElementById('tb').rows(k).bgColor=""; } document.getElementById('tb').rows(++i%document.getElementById('tb').rows.length).bgColor="#FF0000"; document.all.show.value=document.getElementById('tb').rows(i%tb.rows.length).innerText; } } </script>