How to add code to just before closing body tag

Question

How would I put the following code, for a certain shopping cart, just before the closing body tag in my WordPress site? In the footer? It seems to me that I would only want to call startcart() for product pages. Thanks very much.

<script language="javascript" type="text/javascript">
startcart()
</script>

Answer 1

If you're just using a small script or other markup, you can hook a function to the wp_footer filter, which is included in all modern themes:

function wpse_77196_script_in_footer() {
    <script language="javascript" type="text/javascript">
    startcart()
    </script>
}
add_filter( 'wp_footer', 'wpse_77196_script_in_footer' );

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However, if your JavaScript code is more substantial, or you wish to use built-in libraries such as jQuery, you should put the code in an external file, enqueue it properly using the wp_enqueue_script() function:

wp_enqueue_script(
    'myscript', // lowercase name of script
    get_template_directory_uri() . '/js/script.js', // url to script
    array( 'jquery' ), // libraries to use
    false, // version of script (false is WP version)
    true // load in footer (true) or head (false)? 
);

You can read more about how to use the wp_enqueue_script() functon at the Codex

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If you need more help, please post a comment below.