global post variable not working in wordpress plugin - php

Question

I understand that the Wordpress global $post may not work until a certain point because it hasnt been loaded, but Im wondering is there a workaround for this.
Basically Im building a plugin specifically for a client. At the moment the variable is showing nothing.
This code is in a plugin in the plugins folder.
Im looking to make sure it only loads javascript (Ive left out that bit) when on specific pages (selected by the user), at the moment its loading on all pages.
My other option is to do it all on a php template, but to be honest I wanted to write it as a plugin with a view to customizing it for more generic use in the future, plus I have little experience with plugins so Im trying to improve that side of things also.
function include_js() {
global $post;
print_r($post);
if(is_object($post) && $post->ID == 14 ){
// do stuff
wp_enqueue_script('include-map', plugin_dir_url( __FILE__ ) . 'map.js');
}
}
add_action( 'init', 'include_js' );
EDIT: I realised my main issue is that I want to include the javascript and because of that I need wp_enqueue_script , but I can only seem to get that work if you use the init action, which happens before the loop.

Answer 1

After seeing your edit, try hooking to wp_enqueue_scripts instead of init. Like this:
function include_js() {
global $post;
print_r( $post );
if ( is_object( $post ) && $post->ID == 14 ) {
// do stuff
wp_enqueue_script( 'include-map', plugin_dir_url( __FILE__ ) . 'map.js' );
}
}
add_action( 'wp_enqueue_scripts', 'include_js' );
Ref: http://codex.wordpress.org/Plugin_API/Action_Reference/wp_enqueue_scripts

Answer 2

You should test $wp_query->queried_object_id instead of $post->id:
function include_js() {
global $wp_query;
if ( $wp_query->queried_object_id == 14 ) {
// do stuff
//...
}
}
add_action( 'wp_enqueue_scripts', 'include_js' );

Answer 3

There is no need for any globals etc. You can simply use is_single($post) to check if you are on a specific single post and then enqueue your script. You should always always use the wp_enqueue_scripts hook to hook your function to to enqueue scripts and styles
function include_js() {
if(is_single(14)) {
// do stuff
wp_enqueue_script('include-map', plugin_dir_url( __FILE__ ) . 'map.js');
}
}
add_action( 'wp_enqueue_scripts', 'include_js', 999 );
Remeber also, always add priority when adding custom scripts/styles. See add_action( $hook, $function_to_add, $priority, $accepted_args )