2 dimensional matrix in JavaScript

If it doesn't have to be for loops, you can also use map:

var list = [[1, 2, 3], [4, 5, 6], [7, 8, 9]],
    someId = document.getElementById( 'someID' );

someId.innerHTML = '<pre>' + list.map(function (row) {
    return row.join(' '); 
}).join('<br>') + '</pre>';

<div id="someID"></div>

Construct the string to output in the inner loops, and after the outer loop you make your element to show that string.

Something like this iterating through each idea:

add <div id="someID"></div>

Then instead of hard coding 3 use list.length and list[i].length then do:

var list = [[1, 2, 3], [4, 5, 6], [7, 8, 9]];

var temp = "";
for (i = 0; i < list.length; i++) {
    for (j = 0; j < list[i].length; j++) {
       temp+=list[i][j] + " ";
    }
    temp+="<br>";
} 
document.getElementById("someID").innerHTML = temp;

Working JSFiddle: http://jsfiddle.net/0k1tf5wh/

Hope this helps!!

To display it in a div, you'll need to wrap each row in a div, because of how HTML handles whitespace:

See: JSFiddle

var list = [[1, 2, 3], [4, 5, 6], [7, 8, 9]];
var html = '';
for (i = 0; i < list.length; i++) {
    html += list[i].join(' ');
}
document.getElementById('someID').innerHTML = html;

There are many ways to do that.

console.log will print one line per call on most browsers.

You can use line breaking characters ('\n') to print to a file, if you are working on an environment where you have access to IO (i.e.: NodeJS).

In HTML you can use the <br> tag, paragraphs (<p>), or you can place each line in a div. For example, with <br> you could do it like this:

var list = [[1, 2, 3], [4, 5, 6], [7, 8, 9]];

for (i = 0; i < list.length; i++) {
    document.getElementById("someID").innerHTML += list[i].join(" ") + "<br>";
}

Remember that each element of the outer array is an array itself, so you can print them as one element each with the join method from the Array type.