Auto-reset Countdown Timer shortcode

shortcode.php

/**
 * How to use: [my_custom_timer id="my-timer" time="300" placeholder="00:00"]
 */
add_shortcode( 'my_custom_timer', function( $attrs ) {
	// id attribute for the timer HTML.
	$id = isset( $attrs['id'] ) && ! empty( $attrs['id'] ) ? $attrs['id'] : 'my-timer';
  // set the time to start countdown (in seconds).
	$time = isset( $attrs['time'] ) && ! empty( $attrs['time'] ) ? intval( $attrs['time'] ) : 120;
  // default placeholder to appear on load
	$placeholder = isset( $attrs['placeholder'] ) ? $attrs['placeholder'] : '';

	ob_start();
	?>
	<div class="my-custom-timer" id="<?php esc_attr_e( $id ); ?>" data-time="<?php echo $time; ?>"><?php echo $placeholder; ?></div>
	<script>
		;(function($) {
			var init = function() {
				var timeleft = <?php echo $time; ?>, minutes, seconds;
				var timer = setInterval(function() {
					if(timeleft <= 0){
						clearInterval(timer);
						init();
					}
					minutes = (timeleft / 60) | 0;
					seconds = (timeleft % 60) | 0;
				
					minutes = minutes < 10 ? "0" + minutes : minutes;
					seconds = seconds < 10 ? "0" + seconds : seconds;
				
					$("#<?php esc_attr_e( $id ); ?>").html( minutes + ":" + seconds ); 
					timeleft -= 1;
				}, 1000);
			};
			init();
		})(jQuery);
	</script>
	<?php

	return ob_get_clean();
} );