Research about Randomising , need assistance here.

[anson920520]

I am currently, research the randomizing,
and i try to make a minesweeper game to play around with my new function.
My plan is lay ten mines inside the mine table
but after i run my code , i got some unexpected problem which is i can't have
ten random mines everytime i refresh it.
I have fix some loop and code but the problem is still here.

My current lay mines code looks like this :

<script type="text/javascript">
function addmines (x) {
var n = 10; //number of mines
var mines = []; //an empty array
while (n>0) {
var row = Math.floor(1+Math.random()*10);
var col = Math.floor(1+Math.random()*10);

if (row >= 0 && row < 10){
if (col >= 0 && col < 10) {
var id = "r"+ row + "c" + col;

n++;

var a = document.createElement("img");
a.src = "mine32.gif";
a.height = 30;
a.width = 30;
document.getElementById(id).appendChild(a);


}
}

}
return x;
}

</script>



And this is my tables

//Creates Table
document.write('<table>');
//for loop that creates the row, increments from 0 to 9 each time it reiterates
for (var row=0; row<9; row++) {
//creates the table row
document.write('<tr>');
//a nested for loop that reiterates 9 times creating the <td>'s and then exits to the parent for loop.
for (var col=0; col<9; col++) {
//references all the <td>'s with a specific id attribute.
document.write('<td id="r', row, 'c', col, '">');
//document.write('&nbsp;');
//closes the <td>
document.write('</td>');
}
//closes the <tr> or row in plain English
document.write('</tr>');
}
//closes the <table> tag
document.write('</table>');

addmines();


Can someone give me suggestion and assistance that allow me to correct my mistakes please?

[ReFreezed]

There are several issues. First of all, there's an error: you're trying to add an image to a <td> element that doesn't exist. So either too few <td>s are created or the numbers for your random row and column are too high or low. (Always check the console!)

Secondly you're saying n++ instead of n-- which means that the while loop will loop forever. (n>0 will always be true.)

Some unnecessary things that can be removed are the empty mines array and these checks:

if (row >= 0 && row < 10){
if (col >= 0 && col < 10) {

because you already know row and col will be within those boundaries when you set them. The argument variable x is also unused and can be removed.

Here's the fixed code:

function addmines () {
    var n = 10; //number of mines
    while (n>0) {
        var row = Math.floor(Math.random()*9);
        var col = Math.floor(Math.random()*9);

        var id = "r" + row + "c" + col;

        var td = document.getElementById(id);
        if (td.children.length > 0)
            continue; //there's already a mine here

        n--;

        var a = document.createElement("img");
        a.src = "mine32.gif";
        a.height = 30;
        a.width = 30;
        td.appendChild(a);

    }
}

//Creates Tabledocument.write('<table>');
//for loop that creates the row, increments
//from 0 to 9 each time it reiterates
for (var row=0; row<9; row++) {
    document.write('<tr>');
    //a nested for loop that reiterates 9 times creating
    //the <td>'s and then exits to the parent for loop.
    for (var col=0; col<9; col++) {
        document.write('<td id="r', row, 'c', col, '">');
        document.write('</td>');
    }
    document.write('</tr>');
}
document.write('</table>');

addmines();

[anson920520]

Thank you for reply ,
i have fixed it ,
i had a stupid mistake ,
everything is good now , thank you very much