Advanced conditional logic with custom javascript functions

CF7 Conditional Fields PRO 1.6.2 introduces the possibility to write your own JavaScript functions to determine whether or not a group should be shown.

Form

    Sorry, you are too young to watch dirty pictures. Try decreasing your date of birth.

    Hooray! You are older than 18. Here's some explicit content:

    o
    /__o
    _// <
    '

    Form Code

    <label>Date of birth:
[date date-of-birth "2010-04-03"]</label>

[group minus-18]
Sorry, you are too young to watch dirty pictures. Try decreasing your date of birth.

[/group][group plus-18]
Hooray! You are older than 18. Here's some explicit content:
<div style="font-family: monospace;white-space: pre;">    o   <br>   /__o <br> _// &lt; <br>'   </div>
[/group]

    Conditional Fields (Text)

    show [plus-18] if [date-of-birth] function "isOlderThan18"
    
show [minus-18] if [date-of-birth] function "isYoungerThan18"

    In order for the above example to work, you need to create two JavaScript functions – not PHP functions! – called isOlderThan18(field) {} and isYoungerThan18(field) {} in your theme. These functions need to return true or false. Preferably, you need to place these functions somewhere in a custom JS file, or if you must, in your header.php or footer.php, for example before the closing </body> tag in your theme.

    Alternatively, you can also add the JavaScript function directly in your form code at the bottom. Just wrap it with <script></script> and make sure to not include any additional whitespaces if you do this. Because CF7 might transform blank lines to paragraph, resulting in invalid HTML and your code breaking.

    The field parameter passed is the jQuery object of the date field element. If you want to access the DOM field directly, you can get it with field[0].

    For future compatibility We strongly recommend to include the line field = field instanceof jQuery ? field[0] : field; at the beginning of your function, and refrain from using jQuery inside your function. At some point in the future (after jQuery gets removed completely from CF7 or WP core) we will have to change this to the native DOM element. Adding this line to your function will make sure that your forms don’t break when that happens.

    Here’s the full JavaScript code used to check if the user is older or younger than 18:

    <script>

    function isOlderThan18(field) {

        //Add this line for future compatibility:
        field = field instanceof jQuery ? field[0] : field;

        //expected format: yyyy-mm-dd

        var birthdate_str = field.value;
        var dmy = birthdate_str.split("-");

        if (dmy.length !== 3 ||
            isNaN(dmy[0]) || dmy[0].length!==4 ||
            isNaN(dmy[1]) || dmy[1].length!==2 ||
            isNaN(dmy[2]) || dmy[2].length!==2 )
        {
            return false; //invalid format
        }

        var birthdate = new Date(dmy[0], dmy[1] - 1, dmy[2]);

        if (birthdate === "Invalid Date" || isNaN(birthdate))
        {
            return false; // invalid date
        }

        //at this point the date is valid

        if (calculateAge(birthdate) >= 18) {
            return true; // older than 18
        } else {
            return false; // younger than 18
        }

    }

    function isYoungerThan18(field) {
        return !isOlderThan18(field);
    }

    function calculateAge(birthdate) { // birthday is a date
        var ageDifMs = Date.now() - birthdate.getTime();
        var ageDate = new Date(ageDifMs); // miliseconds from epoch
        return Math.abs(ageDate.getUTCFullYear() - 1970);
    }

</script>