How to write a Javascript function inside the functions.php of Wordpress?

Question

I'm altering a plugin on developer recommendations (See latest post), which advices to write a bit of Javascript in the functions.php of Wordpress.

Now, when I did that my whole wordpress went blank. Well, after a bit of thinking.. "You can't write plain Javascript inside of PHP"..

So I wrote them inside a <script> tag, and that inside of a echo ", "; tags. Now.. I'm unsure of the function working (have not tested that yet), but Wordpress is showing again, but.. I'm getting the message

Notice: Undefined variable: group in /home/appelhulp/domains/appelhulp.nl/public_html/wp-content/themes/Divi/functions.php on line 8
Notice: Undefined variable: option in /home/appelhulp/domains/appelhulp.nl/public_html/wp-content/themes/Divi/functions.php on line 9
Notice: Undefined variable: option in /home/appelhulp/domains/appelhulp.nl/public_html/wp-content/themes/Divi/functions.php on line 25

And this is the code file enter image description here

So my question:
What is the problem and how do I make those messages disappear?

The correct answer

Although I accepted @Burak's answer, this is only half of the correct answer. Please also see @RahilWazir's part, which half of his/her answer belongs to the solution. As Burak came with the correct script, RahilWazir came with the suggestion to place it in the footer.php instead of functions.php. And placing it there, did the trick. In functions.php didn't let me achieve what I was seeking. Therefor, thanks both!

You should look into Nowdoc syntax, it’ll make those tedious and error-prone escapings unnecessary – php.net/manual/en/… — C3roe
– C3roe, Commented Jul 5, 2014 at 14:20
@RahilWazir, what you mean with 'What functions.php file'? - It's in the functions.php inside the folder of the installed theme. — Sander Schaeffer
– Sander Schaeffer, Commented Jul 5, 2014 at 14:30

Prince Singh · Accepted Answer · 2014-07-05 14:30:53Z

5

there is a better and standard way in wordpress

<?php
function add_js_functions(){
?>
<script>
// your js functions here 
</script>
<?php
}
add_action('wp_head','add_js_functions');

answered Jul 5, 2014 at 14:30

Prince Singh

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2 Comments

Sander Schaeffer Over a year ago

Where should I write that? You shouldn't nest <?php inside of eachother. Therefor, I assume it's not in the functions.php file? Else you could've removed the <?php tag.

Prince Singh Over a year ago

paste that in functions.php and write your js function in commented place

Community · Accepted Answer · 2023-11-17 20:20:27Z

2

As you are using double quotes, PHP will think that the variable with $ signs as a php variable. You need to either change them to single quote and rearrange the code either you need to take a look at heredoc which is suitable for situations like this.

echo <<<'EOT'
<script>
( function() {
    var categories = {};
    var $group = jQuery();
    jQuery('select.app_select_services option').remove().each(function() {
        var $option = jQuery(this),
            contents = $option.text().split(' - '),
            group = jQuery.trim(contents[1]);

        if (!categories.hasOwnProperty(group)) {
            var optGroup = jQuery('<optgroup />', { label: group });
            optGroup.appendTo('select.app_select_services');
            categories[group] = optGroup;
        }

        categories[group].append(jQuery('<option />', {
            text: jQuery.trim(contents[0]),
            value: jQuery(this).val()
        }));
    });
} )();
</script>
EOT;

edited Nov 17, 2023 at 20:20

CommunityBot

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answered Jul 5, 2014 at 14:21

Burak Ozdemir

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2 Comments

Sander Schaeffer Over a year ago

Well, any error is gone, even the single 0, which I've written in the comments at @orion's answer, below.. However, it seems the function is not working, although I simply copy pasted it from the developers post, in the link above..

Burak Ozdemir Over a year ago

i don't know whether the jQuery function is working as expected or not but this is pasting the function as expected and there is not any syntax errors in jQuery function.

Rahil Wazir · Accepted Answer · 2014-07-16 01:18:17Z

2

You need to wait for DOM to be fully initialized. So wrap your jQuery snippet within ready handler. Or even better place is to place this snippet in your footer.php file before closing </body> tag.

jQuery(document).ready(function($) { // <-- wrap it
    var categories = {};
    var $group = jQuery();
    jQuery('select.app_select_services option').remove().each(function() {
        var $option = jQuery(this),
            contents = $option.text().split(' - '),
            group = jQuery.trim(contents[1]);

        if (!categories.hasOwnProperty(group)) {
            var optGroup = jQuery('<optgroup />', { label: group });
            optGroup.appendTo('select.app_select_services');
            categories[group] = optGroup;
        }

        categories[group].append(jQuery('<option />', {
            text: jQuery.trim(contents[0]),
            value: jQuery(this).val()
        }));
    });
});

edited Jul 16, 2014 at 1:18

answered Jul 5, 2014 at 14:36

Rahil Wazir

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3 Comments

Sander Schaeffer Over a year ago

I did had to wrap it into a <script type="text/javascript">, but now it results in the next error message ->

Notice: Undefined index: page_id in /home/appelhulp/domains/appelhulp.nl/public_html/wp-content/plugins/appointments/includes/widgets.php on line 212

.. - Does that mean the code actually is incorrect?

Rahil Wazir Over a year ago

@SanderSchaeffer This has nothing to to with above code.

Sander Schaeffer Over a year ago

Although I can't place two correct answer marks, please see my update on the OP where I also thank you for your input, which was half of the complete solution. Therefor my gratitude to you!

Lewis · Accepted Answer · 2014-07-05 14:16:09Z

1

When you use double quotes "" to define JS string, PHP will interpret $group as a variable. In order to fix it, you need to use single quotes '' instead.

answered Jul 5, 2014 at 14:16

Lewis

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2 Comments

Sander Schaeffer Over a year ago

Changed " to ', but Wordpress is giving me the following error:

Parse error: syntax error, unexpected T_STRING, expecting ',' or ';' in /home/appelhulp/domains/appelhulp.nl/public_html/wp-content/themes/Divi/functions.php on line 7

Sander Schaeffer Over a year ago

Update: I've changed all ' in the Javascript to double quotes (") and now it's not giving an error, but just 0.. .. - But Wordpress is usable again

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