wp_add_inline_style() – without dependency
The wp_add_inline_style() can be used without a source file dependency.
Here’s an example from @Flix:
wp_register_style( 'dummy-handle', false );
wp_enqueue_style( 'dummy-handle' );
wp_add_inline_style( 'dummy-handle', '* { color: red; }' );
where we would hook this into the wp_enqueue_scripts action.
wp_add_inline_script() – without dependency
According to ticket #43565, similar will be supported for wp_add_inline_script() in version 4.9.95.0 (thanks to @MarcioDuarte, @dev101 and @DaveRomsey for the verification in comments):
wp_register_script( 'dummy-handle-header', '' );
wp_enqueue_script( 'dummy-handle-header' );
wp_add_inline_script( 'dummy-handle-header', 'console.log( "header" );' );
that will display the following in the header, i.e.between the <head>...</head> tags:
<script type="text/javascript">
console.log( "header" );
</script>
To display it in the footer:
wp_register_script( 'dummy-handle-footer', '', [], '', true );
wp_enqueue_script( 'dummy-handle-footer' );
wp_add_inline_script( 'dummy-handle-footer', 'console.log( "footer" );' );
The default of $position input argument in wp_add_inline_script() is 'after'. The 'before' value prints it above 'after'.