How to find a 10% discount of all elements in a JavaScript array

Question

How do I find the discounted price of all the elements? The discount should be 10%

Here is what I have attempted:

    var arr = [299.99, 399.99, 599.99, 799.99]
    arr.forEach((value, index) => {
    arr[index] * (10/100)

});

Answer 1

Map it

  var discount = arr.map(el => el * 0.9);

If you want 2 decimals use toFixed(2)

  var discount = arr.map(el => (el * 0.9).toFixed(2));

The values will convert to string. So parse it back

   var discount = arr.map(el => parseFloat((el * 0.9).toFixed(2)));

Answer 2

When working with money you should use pennies to avoid loss of precision errors.

The following uses Array#Map to calculate the discounted price, and then Number#toFixed to round it to the nearest penny. If this is for production code, then you need to make absolutely sure that this type of rounding is permitted.

 var arr = [299.99, 399.99, 599.99, 799.99] const discount = (arr) => arr.map((el) => (el - el * (10/100)).toFixed(2)) console.log(discount(arr))