Age calculator using JavaScript, CSS Grid and flexbox

Hey,

as you are probably beginner, don't worry that your code is that long, you will improve as you practice. But here are 2 major tips for your programming habits not only js but overall.

1. Separation of concerns Your click function is too long. All of your comment should be functions. It will make code more readable and easier to change
2. Hard coded values If you can, don't use hard coded values. In this code, firstly it is longer then needed and it doesn't cover case when February has 29 days.

 if (monthInput.value == 2 && dayInput.value > 28)

When you can, try to use other methods. Here recommended are inbuilt Date functions that you should explore. This is my example of validating day by inbuilt functions:

  const dayValidator = () => {
    //Checking if day is okay in current year case 
    if (year === currentYear && month === new Date().getMonth() + 1 && day > new Date().getDate()) return false;

    //Checking if day is okay based on particular month length
    if (day >= 1 && day <= new Date(year, month, 0).getDate()) return true;
    else return false;
  };

Yes I got it