Run script on all post page load in WordPress

Question

I want my jQuery script run every time post page is open or loaded. I have tried use echo in script but not work

Where should I put it to make the script run?

single.php

<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.1.0/jquery.min.js"></script>
<?php
/**
 * The template for displaying all single posts and attachments
 *
 * @package WordPress
 * @subpackage Twenty_Fifteen
 * @since Twenty Fifteen 1.0
 */

get_header(); ?>

    <div id="primary" class="content-area">
        <main id="main" class="site-main" role="main">

        <?php
        // Start the loop.
        while ( have_posts() ) : the_post();

            echo "
                <script type=\"text/javascript\">
                alert("hello!"); //placeholder script
                </script>
            ";
            /*
             * Include the post format-specific template for the content. If you want to
             * use this in a child theme, then include a file called called content-___.php
             * (where ___ is the post format) and that will be used instead.
             */
            get_template_part( 'content', get_post_format() );

            // If comments are open or we have at least one comment, load up the comment template.
            if ( comments_open() || get_comments_number() ) :
                comments_template();
            endif;

            // Previous/next post navigation.
            the_post_navigation( array(
                'next_text' => '<span class="meta-nav" aria-hidden="true">' . __( 'Next', 'twentyfifteen' ) . '</span> ' .
                    '<span class="screen-reader-text">' . __( 'Next post:', 'twentyfifteen' ) . '</span> ' .
                    '<span class="post-title">%title</span>',
                'prev_text' => '<span class="meta-nav" aria-hidden="true">' . __( 'Previous', 'twentyfifteen' ) . '</span> ' .
                    '<span class="screen-reader-text">' . __( 'Previous post:', 'twentyfifteen' ) . '</span> ' .
                    '<span class="post-title">%title</span>',
            ) );

        // End the loop.
        endwhile;
        ?>

        </main><!-- .site-main -->
    </div><!-- .content-area -->

<?php get_footer(); ?>

Answer 1

You're not escaping the "Hello" text :

alert("hello!");

Try this instead :

alert('hello!'); // or alert(\"hello!\");

Answer 2

The best way is probably to use fopen

eg

<?php

$filename = "https://ajax.googleapis.com/ajax/libs/jquery/3.1.0/jquery.min.js";
$myfile = fopen($filename, "rb");
if (FALSE === $myfile) {
    exit("Failed to open stream to URL");
}

while (!feof($handle)) {
    $contents = stream_get_contents($myfile, 8192));
}
fclose($myfile);  //close the file again when necessary

?>

You could alternatively reverse the backslashes and echo the script in the traditional way

<?php echo "<script type=\"text/javascript\" src=\"jquery.min.js\"></script>; ?>

Note i haven't completed the jquery path (that's the downside.. it's a long path! .. lots of backslashes..)

Answer 3

I think use your script out of loop in single.php file or try another way.

if( jQuery(".single").hasClass(".single-post") ){
    alert("hello!"); // whatever you want to process.
}

Use this code in your main js file. i think it will help you