JavaScript, function encapsulation exercises, to determine whether the date is valid

Whether the date is legal, you need to understand that leap year and ordinary year February days are not the same, there is a large month and small month days are not the same, with a simple statement or can be achieved, but now the requirement to determine whether the date is legal package a function, parameters are respectively year, month, day. This is a bit difficult, the code is as follows, I did not use the FUNCTION wrapped separately in JS file, easier to observe.

HTML: fiefldSet form field set, add a nice interface, look like this

<fieldset>
        <legend>Is the date valid?</legend>
        <span>Years:</span><input type="text" id="inp1"> <span> </span><input type="text" id="inp3"> <button ID =" BTN ">Copy the code

 <script>
        // Wrap the document.getelementByid () function with a simplified get function
        function get(id) {
            return document.getElementById(id);
        }
        // Encapsulate the leap year. N is the year
        function o_year(n) {
            if (n % 4= =0 && n % 100! =0 || n % 400= =0) {
                return true;
            } else return false;
        }
        // Encapsulate the judgment date with year, month, and day
        function o_date(year, month, day) {
            // Check that the year cannot be empty and cannot be a decimal
            if(year ! ="" && year % 1= =0) {
                // Check whether the month is valid
                if (month <= 12 && month >= 1 && month % 1= =0) {
                    if (month == 1 || month == 3 || month == 5 || month == 7 || month == 8 || month == 10 || month == 12) {
                        // If the month is 31 days, return false
                        if (day <= 31 && day >= 1 && day % 1= =0) {
                            return true;

                        } else return false;
                    }
                    if (month == 4 || month == 6 || month == 9 || month == 11) {
                        // Check whether the month is 30 days
                        if (day <= 30 && day >= 1 && day % 1= =0) {
                            return true;

                        } else return false;
                    }
                    if (month == 2) {
                        // Call the leap year function to determine whether year is a leap year
                        if (o_year(year) == true) {
                            // If February is 29 days, return false
                            if (day >= 1 && day <= 29 && day % 1= =0) {
                                return true;
                            } else return false
                        } else {
                            // If February is 28 days, return false
                            if (day >= 1 && day <= 28 && day % 1= =0) {
                                return true
                            } else return false}}return true;
                } else return false;
            } else return false
        }

        var oInp1 = get('inp1')
        var oInp2 = get('inp2')
        var oInp3 = get('inp3')
        var oBtn = get('btn')
        oBtn.onclick = function() {
            if (o_date(inp1.value, inp2.value, inp3.value) == true) {
                alert("Date valid")}else alert("The date is not valid")
        }
    </script>
Copy the code

The result: Leap years have more than 29 February days, so the date is illegal.