Or, embed this snippet using GenerateWP WordPress Plugin.

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Load Script

// Add Shortcode
function load_js_charlimit() {

	wp_enqueue_script('charlimit', get_stylesheet_directory_uri() . '/js/charlimit.js', array('jquery'), '', true);
	// https://www.jqueryscript.net/form/jQuery-Plugin-To-Restrict-The-Number-of-Characters-In-Text-Fields-CharLimit.html

}
add_shortcode( 'charlimit', 'load_js_charlimit' );