Update Cart on Quantity Change

gistfile1.txt

add_action( 'wp_head', function() {

	?><style>
	.woocommerce button[name="update_cart"],
	.woocommerce input[name="update_cart"] {
		display: none;
	}</style><?php
	
} );

add_action( 'wp_footer', function() {
	
	?><script>
	jQuery( function( $ ) {
		let timeout;
		$('.woocommerce').on('change', 'input.qty', function(){
			if ( timeout !== undefined ) {
				clearTimeout( timeout );
			}
			timeout = setTimeout(function() {
				$("[name='update_cart']").trigger("click");
			}, 500 );
		});
	} );
	</script><?php
	
} );