Q:

Javascript nested array with nested loops

I created a nested array as I could so far but I feel like i did it wrong or something does not make sense. Could anyone please have a look and tell me if my array is the way to build nested array. All I want is to create rows under specific title, so I nested data and calling it with nested loops. Maybe theres is a simpler way of achiving it. Here is the code:
var data = [

    {title:'Row Title 1'},

    [{leftCol:'Some text for left column',rightCol:'Some text for right column'},
    {leftCol:'Some text for left column',rightCol:'Some text for right column'},
    {leftCol:'Some text for left column',rightCol:'Some text for right column'}],

    {title:'Row Title 2'},

    [{leftCol:'Some text for left column',rightCol:'Some text for right column'},
    {leftCol:'Some text for left column',rightCol:'Some text for right column'},
    {leftCol:'Some text for left column',rightCol:'Some text for right column'}]

    ];

    for (var i=0, j=data.length; i < j; i++) {

        if(data[i].title != null){
            document.write('<b>'+data[i].title+'</b><br />');
        }

        for(p=0,plen=data[i].length; p<plen;p++){
            document.write('<p style="background:#eee;">'+data[i][p].leftCol+'</p>');
            document.write('<p>'+data[i][p].rightCol+'</p>');       
        }
    }

A:

The structure you're using should be more like this:
var data = [

    {title:'Row Title 1', contents: [

      {leftCol:'Some text for left column',rightCol:'Some text for right column'},
      {leftCol:'Some text for left column',rightCol:'Some text for right column'},
      {leftCol:'Some text for left column',rightCol:'Some text for right column'}

    ],

    // ...
];

That way, each row is an object with a "title" attribute and a "contents" attribute.  Your loop would then look like this:
for (var i=0, j=data.length; i < j; i++) {

    if(data[i].title != null){
        document.write('<b>'+data[i].title+'</b><br />');
    }

    for(var p=0, plen=data[i].contents.length; p < plen; p++){
        document.write('<p style="background:#eee;">'+data[i].contents[p].leftCol+'</p>');
        document.write('<p>'+data[i].contents[p].rightCol+'</p>');       
    }
}

