Example of is_new

sample-plugin.php

<?php
/*
Plugin Name: Sample Plugin
Plugin URI: https://brianhogg.com/
Description: Showing is_new
Version: 1.0
Author: Brian Hogg
Author URI: https://brianhogg.com
License: GPLv2 or later
*/

define( 'SAMPLE_VERSION', 1 );

function my_sample_enqueue_script() {
	if ( !is_page( 'about' ) )
		return;

	wp_enqueue_script(
		'my-sample-script',
		plugins_url( 'js/sample.js', __FILE__ ),
		array( 'jquery' ),
		SAMPLE_VERSION,
		true
	);

	wp_localize_script(
		'my-sample-script',
		'sample_data',
		array(
			'is_new' => strtotime(get_post()->post_date) > strtotime('-7 days'),
		)
	);
}
add_action( 'wp_enqueue_scripts', 'my_sample_enqueue_script' );