how to find digits on double place number in number javascript code example

Example 1: rounding number to x decimals javascript

let num = 12.5452411;
num = num.toFixed(3); // 12.545

Example 2: how to numeric value is after point 2 values in javascript

var totalAmount = 0;
totalAmount = Number($("#sub_amount").val()) + Number($("#vat_amount").val());
totalAmount = totalAmount.toFixed(2);
$('#total_amount').val(totalAmount);
//@sujay