Copy the function below and paste it into your functions.php file:
function is_blog() { if (is_home() || is_singular('post') || is_post_type_archive('post')) return true; else return false; }
Once done, you can use the function to detect if you’re currently on a blog related page:
<?php if(is_blog()) { //the page is blog related } ?>
Thanks to Nathan for the tip!