<!DOCTYPE html>
<html lang="en"><head>
	<meta charset="utf-8">
	<meta name="viewport" content="width=device-width, initial-scale=1">
	<title>jQuery UI Autocomplete - Combobox</title>
	<link rel="stylesheet" href="https://code.jquery.com/ui/1.14.1/themes/base/jquery-ui.css">
	<style>
    body {
        font-family: Arial, Helvetica, sans-serif;
    }

    table {
        font-size: 1em;
    }

    .ui-draggable, .ui-droppable {
        background-position: top;
    }
	.custom-combobox {
		position: relative;
		display: inline-block;
	}
	.custom-combobox-toggle {
		position: absolute;
		top: 0;
		bottom: 0;
		margin-left: -1px;
		padding: 0;
	}
	.custom-combobox-input {
		margin: 0;
		padding: 5px 10px;
	}
	</style>
	<script src="https://code.jquery.com/jquery-3.7.1.js"></script>
	<script src="https://code.jquery.com/ui/1.14.1/jquery-ui.js"></script>
	<script>
	$(document).ready(() => {
		$.widget( "custom.combobox", {
			options: {
    			data: []
  			},

			_create: function() {
				this.wrapper = $( "<span>" )
					.addClass( "custom-combobox" )
					.insertAfter( this.element );

				this.element.hide();
				this._createAutocomplete();
				this._createShowAllButton();
			},

			_createAutocomplete: function() {
				var selected = this.element.children( ":selected" ),
					value = selected.val() ? selected.text() : "";

				this.input = $( "<input>" )
					.appendTo( this.wrapper )
					.val( value )
					.attr( "title", "" )
					.addClass( "custom-combobox-input ui-widget ui-widget-content ui-state-default ui-corner-left" )
					.autocomplete({
						delay: 0,
						minLength: 0,
						source: this._source.bind( this )
					})
					.tooltip({
						classes: {
							"ui-tooltip": "ui-state-highlight"
						}
					});

				this._on( this.input, {
					autocompleteselect: function( event, ui ) {
						if (this.element.is("select")) {
						    if (ui.item.option) {
							    ui.item.option.selected = true;
						    }
						} else if (this.element.is("input")) {
						    this.element.val(ui.item.value || ui.item.label);
						}
						this._trigger( "select", event, {
							item: ui.item.option
						});
					},
				});
			},

			_createShowAllButton: function() {
				var input = this.input,
					wasOpen = false;

				$( "<a>" )
					.attr( "tabIndex", -1 )
					.attr( "title", "Show All Items" )
					.tooltip()
					.appendTo( this.wrapper )
					.button({
						icon: "ui-icon-triangle-1-s",
						showLabel: false
					})
					.removeClass( "ui-corner-all" )
					.addClass( "custom-combobox-toggle ui-corner-right" )
					.on( "mousedown", function() {
						wasOpen = input.autocomplete( "widget" ).is( ":visible" );
					})
					.on( "click", function() {
						input.trigger( "focus" );

						// Close if already visible
						if ( wasOpen ) {
							return;
						}

						// Pass empty string as value to search for, displaying all results
						input.autocomplete( "search", "" );
					});
			},

			_stripAccents: function (s) {
                if (!s) return "";
                return s
                  .normalize("NFD")
                  .replace(/[u0300-u036f]/g, "")
                  .replace(/đ/g, "d")
                  .replace(/Đ/g, "D");
             },

            _source: function (request, response) {
                var term = this._stripAccents(request.term).toLowerCase();
				var data = this.options.data || [];

				var results = $.map(data, (item) => {
					var label = item.label || item.toString();
					var value = item.value || label;
					var norm = this._stripAccents(label).toLowerCase();

					if (!term || norm.indexOf(term) !== -1) {
						return { label: label, value: value, data: item };
					}
				});
				response(results);
            },

			_destroy: function() {
				this.wrapper.remove();
				this.element.show();
			}
		});

		$("#country").combobox({
			data: [
			    { label: "Hà Nội", value: "Hà Nội" },
			    { label: "TP Hồ Chí Minh", value: "TP Hồ Chí Minh" },
			    { label: "Đà Nẵng", value: "Đà Nẵng" }
			]
	  	});
	  	$("#province").combobox({
			data: [
			    { label: "Long Biên", value: "Long Biên" },
			    { label: "Nghi tàm", value: "Nghi tàm" },
			]
	  	});
	} );
	</script>
</head>
<body>
<input type="text" name="country" id="country">
<input type="text" name="province" id="province">
</body>
</html>