I'm trying to get a value and pass it to a hidden input in order to send form data via $_POST. I have a dropdown button and the following code in order to update the value:

    jQuery(document).ready(function($){
        
        var espSeleccionada = $('button[data-id="select-especialidad"]');
        espSeleccionada.on("click", function() {
            // if changed to, for example, the last option, then
            // $(this).find('option:selected').text() == D
            // $(this).val() == 4
            // get whatever value you want into a variable
            var x = $(this).text();
            // and update the hidden input's value
            $('#boton-prueba').text(x);
        });
    
    });

Please note that I'm using .text() to test if the code works, but it would have .val() before going live.

This is the button HTML:

    <button type="button" class="btn dropdown-toggle btn-default" data-toggle="dropdown" data-id="select-especialidad" title="Hacienda" aria-expanded="false"><span class="filter-option pull-left">Hacienda</span></button>

[Here][1] is an example.


  [1]: https://fiddle.jshell.net/t9mvoxj5/

**EDIT TO CLARIFY HOW I AM ADDING THE CODE TO IN WORDPRESS:**

I add the script via functions.php. This is my code:

    function loading_my_scripts() {
    	wp_enqueue_style( 'buscopreparador-style', get_stylesheet_uri() );
    	wp_deregister_style( 'buscopreparador-style' );
    
    	if ( !is_admin() ) {
    		
    		wp_enqueue_style( 'styles', get_template_directory_uri() . '/assets/css/styles.css' );
    		wp_enqueue_style( 'vertical-tabs', get_template_directory_uri() . '/assets/css/bootstrap.vertical-tabs.min.css' );
        	wp_enqueue_style('bootstrap-select-css', 'https://cdnjs.cloudflare.com/ajax/libs/bootstrap-select/1.10.0/css/bootstrap-select.min.css' );
        	wp_enqueue_style( 'open-sans', 'https://fonts.googleapis.com/css?family=Open+Sans:400,600,600italic,400italic,700,700italic');
    
        	wp_deregister_script( 'jquery' );
    	   	wp_register_script('jquery', 'https://ajax.googleapis.com/ajax/libs/jquery/1.11.3/jquery.min.js', false, false, TRUE );
        	wp_register_script('bootstrap', 'https://maxcdn.bootstrapcdn.com/bootstrap/3.3.6/js/bootstrap.min.js', false, false, TRUE );
        	wp_register_script('bootstrap-tabcollapse', get_template_directory_uri() . '/assets/js/bootstrap-tabcollapse.js', false, false, TRUE );
        	wp_register_script('bootstrap-select', 'https://cdnjs.cloudflare.com/ajax/libs/bootstrap-select/1.10.0/js/bootstrap-select.min.js', false, false, TRUE );
        	wp_register_script('theme-js', get_template_directory_uri() . '/assets/js/theme.js', array('jquery'), false, TRUE );
    
            wp_enqueue_script( 'jquery' );
            wp_enqueue_script( 'bootstrap' );
            wp_enqueue_script( 'bootstrap-tabcollapse' );
            wp_enqueue_script( 'bootstrap-select' );
            wp_enqueue_script( 'theme-js' );
        }
    
    	if ( is_singular() && comments_open() && get_option( 'thread_comments' ) ) {
    		wp_enqueue_script( 'comment-reply' );
    	}
    }
    add_action( 'wp_enqueue_scripts', 'loading_my_scripts' );

The code is in **theme.js** file which looks like this:

    ( function( $ ) {
        var num_cols = 3,
        container = $('#menu-preparadores-de-oposiciones-en'),
        listItem = 'li',
        listClass = 'sub-list';
        container.each(function() {
            var items_per_col = new Array(),
            items = $(this).find(listItem),
            min_items_per_col = Math.floor(items.length / num_cols),
            difference = items.length - (min_items_per_col * num_cols);
            for (var i = 0; i < num_cols; i++) {
                if (i < difference) {
                    items_per_col[i] = min_items_per_col + 1;
                } else {
                    items_per_col[i] = min_items_per_col;
                }
            }
            for (var i = 0; i < num_cols; i++) {
                $(this).append($('<ul ></ul>').addClass(listClass));
                for (var j = 0; j < items_per_col[i]; j++) {
                    var pointer = 0;
                    for (var k = 0; k < i; k++) {
                        pointer += items_per_col[k];
                    }
                    $(this).find('.' + listClass).last().append(items[j + pointer]);
                }
            }
        });
    
        var espSeleccionada = $('button[data-id="select-especialidad"]');
        espSeleccionada.on("click", function() {
            // if changed to, for example, the last option, then
            // $(this).find('option:selected').text() == D
            // $(this).val() == 4
            // get whatever value you want into a variable
            var x = $(this).html();
            // and update the hidden input's value
            $('#boton-prueba').html(x);
        });
    
        if ($("body").hasClass("page-id-64")) {
          $('.tab-content').addClass('col-sm-9');
          $('#custom-tabs-0').tabCollapse();
        };  
    
    } ) ( jQuery );
    
    jQuery(document).ready(function($){
        
        var espSeleccionada = $('button[data-id="select-especialidad"]');
        espSeleccionada.on("click", function() {
            // if changed to, for example, the last option, then
            // $(this).find('option:selected').text() == D
            // $(this).val() == 4
            // get whatever value you want into a variable
            var x = $(this).html();
            // and update the hidden input's value
            $('#boton-prueba').html(x);
        });
    
    }); 
    /**
     * Theme Customizer enhancements for a better user experience.
     *
     * Contains handlers to make Theme Customizer preview reload changes asynchronously.
     */
    
    ( function( $ ) {
    	// Site title and description.
    	wp.customize( 'blogname', function( value ) {
    		value.bind( function( to ) {
    			$( '.site-title a' ).text( to );
    		} );
    	} );
    	wp.customize( 'blogdescription', function( value ) {
    		value.bind( function( to ) {
    			$( '.site-description' ).text( to );
    		} );
    	} );
    	// Header text color.
    	wp.customize( 'footer_copyright', function( value ) {
    		value.bind( function( to ) {
    			$( '.site-info' ).text( to );
    		} );
    	} );
    	// Header text color.
    	wp.customize( 'header_textcolor', function( value ) {
    		value.bind( function( to ) {
    			if ( 'blank' === to ) {
    				$( '.site-title, .site-description' ).css( {
    					'clip': 'rect(1px, 1px, 1px, 1px)',
    					'position': 'absolute'
    				} );
    			} else {
    				$( '.site-title, .site-description' ).css( {
    					'clip': 'auto',
    					'color': to,
    					'position': 'relative'
    				} );
    			}
    		} );
    	} );
    } )( jQuery );
    
    ( function() {
    	var is_webkit = navigator.userAgent.toLowerCase().indexOf( 'webkit' ) > -1,
    	    is_opera  = navigator.userAgent.toLowerCase().indexOf( 'opera' )  > -1,
    	    is_ie     = navigator.userAgent.toLowerCase().indexOf( 'msie' )   > -1;
    
    	if ( ( is_webkit || is_opera || is_ie ) && document.getElementById && window.addEventListener ) {
    		window.addEventListener( 'hashchange', function() {
    			var id = location.hash.substring( 1 ),
    				element;
    
    			if ( ! ( /^[A-z0-9_-]+$/.test( id ) ) ) {
    				return;
    			}
    
    			element = document.getElementById( id );
    
    			if ( element ) {
    				if ( ! ( /^(?:a|select|input|button|textarea)$/i.test( element.tagName ) ) ) {
    					element.tabIndex = -1;
    				}
    
    				element.focus();
    			}
    		}, false );
    	}
    })();