multidimensional arrays in JavaScript is known as arrays inside another array. We need to put some arrays inside an array, then the total thing is working like a multidimensional array. The array, in which the other arrays are going to insert, that array is use as the multidimensional array in our code. 

syntax

array name[
            [1st dimension],
            [2nd dimension],
            [3rd dimension],
            .
            .
            [Nth dimension] 
          ];

example

<!DOCTYPE html>
<html>
<head>
		<title> alert in javascript</title>
</head>
<body>
		<script>
		var array=[
					["shivani",  "female" ,"20"],
					["ravi",  "male",  "18"],
					["abhiprit"  ,"male",  "30"],
					["omprakash", "male", "12"],
					["khushbu",  "female",  "22"],
					["shiv", "male",  "20"]
				  ];
		
		for(var a=0; a<6; a++)
		{
		document.write(array[a] + "<br>");
		}
		
		</script>

</body>
</html>

output

shivani,female,20
ravi,male,18
abhiprit,male,30
omprakash,male,12
khushbu,female,22
shiv,male,20