Get and delete data from array in array
<p>I ran into a little bit of a problem with manipulation of data, since I don't know JavaScript too well. I have the following array:</p>

<pre><code>var Dict = [["x", "y", "z"], ["x", "w", "m"], ["u", "t", "d", "L"]];
</code></pre>

<p>What I need is to select all first elements, then all the second elements etc. I've tried </p>

<pre><code>for(var m in Dict) {
    First.push(m[0]);
    Second.push(m[1]);
    Third.push(m[2]);
}
</code></pre>

<p>But that doesn't seem to work. Then I also need to delete for example all "x" from the top array, which I haven't even attempted yet, because of the first problem.</p>