Explain me these codes ...

Question

private var mineField:Array=new Array();
public function Main() {
// mine field creation
for (var i:uint=0; i<FIELD_H; i++) {
mineField[i]=new Array();
for (var j:uint=0; j<FIELD_W; j++) {
mineField[i].push(0);
trace("Row "+i+": "+mineField[i]);
trace("The whole mine field: "+mineField);
// end of mine field creation
This is a system of multiple array. I copied it from the book of game design. I would like you to explain :
"Why in the trace ""whole mine field" is 81 zeros?"
Ok, I predict (I understood from the book), that private var mineField array is array of i and j
I also understood that mineField[i] is an array containing only the i from loop ("0,1,2,3,4,5,6,7,8")
... and mineField[i].push(0) changes all i-s in array to 0 ?
Please, explain, it all mixes in my head together

Answer 1

I presume FIELD_H and FIELD_W are being set up as const variables somewhere else and you're just pasting relevant code. So I'll reply with the same.
What I think you're looking for is to get 9 rows with 9 columns, each creating a random amount of mines. The value should be 0 for no mine or 1 for a mine. You'd just need to rewrite the push(0) so it generated a 0 or a 1.
e.g.:
private var mineField:Array = new Array();
public function Main()
          // mine field creation
          for (var i:uint = 0; i < FIELD_H; i++)
                    mineField[i] = new Array();
                    for (var j:uint = 0; j < FIELD_W; j++)
                              mineField[i].push(Math.round(Math.random()*1));
                    trace("Row " + i + ": " + mineField[i]);
          trace("The whole mine field: " + mineField);
          // end of mine field creation
Now a number between 0 and 1 will populate each slot. If you want it to be another value range like 0 - 100 then simply change it to: Math.round(Math.random()*100)