A simple for loop executes a specified number of times depending on the initialization value and the terminating condition. A nested for loop on the other hand, resides one or more for loop inside an outer for loop.
In a nested loop the statement inside the for loop body is again a for loop. This causes The inside for loop to execute all the way through , for each iteration of the outer for loop.
for(let i = 0 ; i < limit; i++)
{
for(let j = 0 ; j < limit; j++)
{
// statement
}
// statement for outer loop
}
The inside loop in this example runs limit number of times for every iteration of the outer loop. So, in total, the loop runs limit x limit number of times.
<!DOCTYPE html>
<html>
<head>
<title>JavaScript</title>
<script>
for(var a = 1; a <= 5; a++){
for(var b = 1; b <= a ; b++){
document.write(a + " ");
}
document.write("<br>");
}
</script>
</head>
<body>
</body>
</html>