Javascript traverses elements in table sample code_javascript skills

For example:

<table id=tb>
　<tr><th> </th><th> </th><th> </th><th> </th></tr>
　<tr><td> </td><td> </td><td> </td><td> </td></tr>
　<tr><td> </td><td> </td><td> </td><td> </td></tr>
</table>

How to traverse assignment in JS?
Program code

var count=0;
for(i=0; i < document.getElementById("tb1").rows.length; i++)
{
　　for(j=0; j < document.getElementById("tb1").rows(i).cells.length; j++)
　　{
　　　　document.all.getElementById("tb1").rows(i).cells(j).innerText = count;
　　　　count++;
　　}
}

I saw another way to use dom (but I didn’t try it myself, I don’t know why)

<table id="mylist">
<tr><td>一个和尚有水喝。</td></tr>
<tr><td>两个和尚挑水喝。</td></tr>
<tr><td>三个和尚没水喝。</td></tr>
</table>
<script>
var msg=””
var mylist=document.getElementByIdx("mylist")
for (i=0; i<mylist.childNodes.length; i++){
var tr=mylist.childNodes[i];
for(j=0;j<tr.childNodes[j].length; j++) {
var td=tr.childNodes[j];
msg+=td.innerText;
}
}
alert(msg);
</script>