# Picking Random Item in a Multi-dimensional Array

**URL:** <https://forum.kirupa.com/t/picking-random-item-in-a-multi-dimensional-array/640802>\
**Category:** web dev\
**Created:** [October 10, 2019, 1:29am UTC](https://forum.kirupa.com/t/picking-random-item-in-a-multi-dimensional-array/640802 "2019-10-10T01:29:14Z")\
**Posts on this page:** 6\
**Page:** 1

<div class="post-metadata">

**Author:** ![v\_vendetta](https://yyz1.discourse-cdn.com/flex011/user_avatar/forum.kirupa.com/v_vendetta/32/10212_2.png) [@v\_vendetta](https://forum.kirupa.com/u/v_vendetta)\
**Post date:** [October 10, 2019, 1:29am UTC](https://forum.kirupa.com/t/picking-random-item-in-a-multi-dimensional-array/640802/1 "2019-10-10T01:29:14Z")

</div>

Newbie here!!! Just want to ask on how to insert random placement in this code and make a server on it…I include some jquery file for game instructions also but this is the main reason why I am asking for help. Problem: random placement, connect to AI opponent…or only the random placement.

```javascript
// get the container element
var battletanksID = document.getElementById("battletanks");

// set rows and columns
var rows = 7;
var cols = 7;

// make the grid columns and rows
for (i = 0; i < cols; i++) {
	for (j = 0; j < rows; j++) {
		
		// create a new div HTML element for each grid box
		var box = document.createElement("box");
		battletanksID.appendChild(box);

		// give each div element a unique id based on its row and column
		box.id = 's' + j + i;			

		// set each grid box size. Multiply the size from the current row or column
		var size = 50;
		var topPosition = j * size;
		var leftPosition = i * size;			
		box.style.top = topPosition + 'px';
		box.style.left = leftPosition + 'px';						
	}
}

var missilecount = 10;

//tank placement
var placement = [
				[0,0,0,0,0,0,0],
				[0,0,0,0,0,0,0],
				[0,0,0,1,0,0,0],
				[0,0,0,0,0,0,0],
				[0,0,0,0,0,0,0],
				[0,0,1,0,0,0,0],
				[0,0,0,0,0,0,0]
				]

//add an event listener that fires when a user clicks a square
battletanksID.addEventListener("click", missiles);

function missiles(m) {
    // if item clicked (e.target) is not the parent element on which the event listener was set
	if (m.target !== m.currentTarget) {
        // extract row and column # from the HTML element's id
		var row = m.target.id.substring(1,2);
		var col = m.target.id.substring(2,3);
				
		// if player clicks the box and missed hit
		if (placement[row][col] == 0) {
			m.target.style.background = '#e6e6e6';
			// set box's value to 3 to indicate missed hit
			placement[row][col] = 3;
			//every missed hit it deduct missiles
			missilecount--;
			alert("Missed hit, Try again!");
		}	
		// if player clicks the box and hit the enemies tank
		if (placement[row][col] == 1) {
			m.target.style.background = '#006600';
			// set box's value to 2 to indicate hit target
			placement[row][col] = 2;
			//increment missiles each time tank is hit
			missilecount++;	
			
			//if player hit the tank
			if (missilecount == missilecount++) {
				alert("Enemies tank is defeated!");
				//redirect to Win page
				location.replace("2.html");
			}
		 }
		//if missiles run out
		if(missilecount == 0){
			alert("game over!");
			//redirect to Lose page
			location.replace("3.html");
		}
    }
}

//Jquery
$(document).ready(function(){
	//Hit
	$("#btn2").click(function(){
		$("#btn2").removeClass("btn2");
		$(this).addClass("btn2");
	});
	//Missed Hit
	$("#btn3").click(function(){
		$("#btn3").removeClass("btn3");
		$(this).addClass("btn3");
	});
});

```

---

<div class="post-metadata">

**Author:** ![kirupa](https://yyz1.discourse-cdn.com/flex011/user_avatar/forum.kirupa.com/kirupa/32/11616_2.png) [@kirupa](https://forum.kirupa.com/u/kirupa)\
**Post date:** [October 10, 2019, 3:41am UTC](https://forum.kirupa.com/t/picking-random-item-in-a-multi-dimensional-array/640802/2 "2019-10-10T03:41:08Z")

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You have a multidimensional array for `placement`. Are you looking for how to pick a random spot from inside here as if it were a 7x7 grid?

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<div class="post-metadata">

**Author:** ![v\_vendetta](https://yyz1.discourse-cdn.com/flex011/user_avatar/forum.kirupa.com/v_vendetta/32/10212_2.png) [@v\_vendetta](https://forum.kirupa.com/u/v_vendetta)\
**Post date:** [October 10, 2019, 4:03am UTC](https://forum.kirupa.com/t/picking-random-item-in-a-multi-dimensional-array/640802/3 "2019-10-10T04:03:42Z")

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Yes sir but i don’t know how to executive that code

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<div class="post-metadata">

**Author:** ![kirupa](https://yyz1.discourse-cdn.com/flex011/user_avatar/forum.kirupa.com/kirupa/32/11616_2.png) [@kirupa](https://forum.kirupa.com/u/kirupa)\
**Post date:** [October 10, 2019, 6:23am UTC](https://forum.kirupa.com/t/picking-random-item-in-a-multi-dimensional-array/640802/4 "2019-10-10T06:23:00Z")

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I am not in front of a large screen right now, but the way you can do that is by picking a two random numbers ([https://www.kirupa.com/html5/random\_numbers\_js.htm](https://www.kirupa.com/html5/random_numbers_js.htm)) between 0 and 6. These correspond to the horizontal and vertical positions in your 7x7 grid.

With these two random numbers (let us call them `randomX` and `randomY`), you can do something as follows: `placement[randomY][randomX]`

Does this help? 😀

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<div class="post-metadata">

**Author:** ![v\_vendetta](https://yyz1.discourse-cdn.com/flex011/user_avatar/forum.kirupa.com/v_vendetta/32/10212_2.png) [@v\_vendetta](https://forum.kirupa.com/u/v_vendetta)\
**Post date:** [October 10, 2019, 7:36am UTC](https://forum.kirupa.com/t/picking-random-item-in-a-multi-dimensional-array/640802/5 "2019-10-10T07:36:13Z")

</div>

thanks for the effort sir but still can’t figure it out

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<div class="post-metadata">

**Author:** ![kirupa](https://yyz1.discourse-cdn.com/flex011/user_avatar/forum.kirupa.com/kirupa/32/11616_2.png) [@kirupa](https://forum.kirupa.com/u/kirupa)\
**Post date:** [October 10, 2019, 5:35pm UTC](https://forum.kirupa.com/t/picking-random-item-in-a-multi-dimensional-array/640802/6 "2019-10-10T17:35:50Z")

</div>

Here is a snippet that might help 🙂

```
var placement = [
  [0, 0, 0, 0, 0, 0, 0],
  [0, 0, 0, 0, 0, 0, 0],
  [0, 0, 0, 1, 0, 0, 0],
  [0, 0, 0, 0, 0, 0, 0],
  [0, 0, 0, 0, 0, 0, 0],
  [0, 0, 1, 0, 0, 0, 0],
  [0, 0, 0, 0, 0, 0, 0]
];

var xPosition = Math.floor(Math.random() * placement.length);
var yPosition = Math.floor(Math.random() * placement.length);

console.log(xPosition + "," + yPosition + " :" + placement[yPosition][xPosition]); 

```

🙂