Load main.js from child theme

function.php

function custom_enq_childminjs() {
 	wp_dequeue_script( 'dt-main', get_template_directory_uri() . '/js/main.js', array( 'jquery' ), false, true );

	wp_register_script('dt-main', get_stylesheet_directory_uri() . '/js/main.js', array('jquery'),false, true);
	wp_enqueue_script('dt-main');

}

add_action( 'wp_enqueue_scripts', 'custom_enq_childminjs' ); 

Code goes in child theme functions.php