<!DOCTYPE HTML>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<title>二维数组</title>
<script type="text/javascript">
var myarr=new Array();
for (var i=1;i<4;i++)
{
myarr[i]=new Array();
for(var j=1;j<7;j++){
myarr[i][j]=i*j
document.write(myarr[2][5])
}
}
</script>
</head>
<body>
</body>
</html> 
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Solution, why there is no result-PHP Chinese website Q&A-Solution, why there is no result-PHP Chinese website Q&A
Look around and learn.
当 i=1 时就输出了myarr[2][5]，这个时候还没有myarr[2][5]，把document.write(myarr[2][5])放到循环结束之后即可。
var myarr=new Array(); for (var i=1;i<4;i++) { myarr[i]=new Array(); for(var j=1;j<7;j++){ myarr[i][j]=i*j; } } document.write(myarr[2][5]);