ComboBox

Dynamic suggestions as users type in an input field.

Contents

• Overview
• Installation
• Basic usage
• Configuration Options
• JavaScript API
• Events
• Common Patterns
• License

Overview

The ComboBox component provides an autocomplete input field with dynamic suggestions. It supports both client-side filtering and API-based data fetching, customizable templates, and flexible data rendering options.

Key Features:

• Dynamic autocomplete suggestions
• Client-side and API-based data fetching
• Customizable item templates
• Keyboard navigation support
• Programmatic control via JavaScript API
• Event system for selection tracking
• Accessibility attributes (ARIA) built-in

Installation

To get started, install ComboBox plugin via npm, else you can skip this step if you are already using Preline UI as a package.

npm i @preline/combobox

CSS

Use @source to register the plugin's JavaScript path for Tailwind CSS scanning, then @import the plugin's CSS files into your Tailwind CSS file.

@import "tailwindcss";

/* @preline/combobox */
@source "../node_modules/@preline/combobox/*.js";
@import "./node_modules/@preline/combobox/variants.css";
@import "./node_modules/@preline/combobox/theme.css";

JavaScript

Include the JavaScript that powers the interactive elements near the end of your </body> tag:

<script src="./node_modules/@preline/combobox/index.js"></script>

Manual Initialization

Use the non-auto entry if you need manual initialization. In this mode, automatic initialization on page load is not included, so the component should be initialized explicitly.

<script type="module">
  import HSCombobox from "@preline/combobox/non-auto.mjs";

  new HSCombobox(document.querySelector("#combobox"));
</script>

Via Bundler

When using a bundler (Vite, webpack, etc.), import the plugin directly as an ES module.

@preline/combobox is the auto-init entry: it scans the DOM and initializes matching elements automatically.

import "@preline/combobox";

@preline/combobox/non-auto is the manual entry: use it when you want explicit control over when initialization happens, either via autoInit() or by creating a specific instance yourself.

import HSCombobox from "@preline/combobox/non-auto";

HSCombobox.autoInit();

// Or initialize a specific element manually
const el = document.querySelector("#combobox");
if (el) new HSCombobox(el);

TypeScript

This package ships with TypeScript type definitions. No additional @types/ package is needed.

Basic usage

The following example demonstrates the minimal HTML structure required for a combobox component. This is a base template without custom styling - you can apply your own CSS classes and styles as needed. The combobox shows suggestions as the user types.

<div class="inline-flex relative" data-hs-combo-box>
  <div class="relative">
    <input type="text" role="combobox" aria-expanded="false" value="" data-hs-combo-box-input />
  </div>
  
  <div class="absolute z-50" style="display: none;" data-hs-combo-box-output>
    <div class="cursor-pointer" tabindex="0" data-hs-combo-box-output-item>
      <span data-hs-combo-box-search-text="1" data-hs-combo-box-value>1</span>
    </div>
    <div class="cursor-pointer" tabindex="1" data-hs-combo-box-output-item>
      <span data-hs-combo-box-search-text="2" data-hs-combo-box-value>2</span>
    </div>
  </div>
</div>

Structure Requirements:

• data-hs-combo-box: Required on the container element
• data-hs-combo-box-input: Required on the input element
• data-hs-combo-box-output: Required on the dropdown container
• data-hs-combo-box-output-item: Required on each suggestion item
• data-hs-combo-box-search-text: Required on the searchable text element within each item
• Proper ARIA attributes (role="combobox", aria-expanded)

Initial State:

• Set aria-expanded="false" on the input initially
• Add style="display: none;" to the output container initially
• Output visibility is controlled by the plugin

Configuration Options

Data Options

Data options are specified in the data-hs-combo-box attribute and various data attributes.

| Attribute | Target Element | Type | Default | Description | | --- | --- | --- | --- | --- | | data-hs-combo-box | Container | - | - | Activate a ComboBox by specifying on an element. Should be added to the container. | | :gap | Inside data-hs-combo-box | number | 5 | Determines the indent from the input field to the dropdown list in pixels. | | :viewport | Inside data-hs-combo-box | string | HTMLElement | null | Determines which element will be the parent when calculating the position of the dropdown list. By default it is calculated relative to the document. | | :minSearchLength | Inside data-hs-combo-box | number | 0 | Specifies the minimum number of characters that must be entered before the search function becomes active. | | :apiUrl | Inside data-hs-combo-box | string | null | null | Specifies the API address for fetching suggestions. | | :apiDataPart | Inside data-hs-combo-box | string | null | null | Determines which part of the returned data will be taken as the main data array. If this parameter is empty, then the root is taken as a basis. | | :apiQuery | Inside data-hs-combo-box | string | null | null | Defines request parameters, such as limit. | | :apiSearchQuery | Inside data-hs-combo-box | string | null | null | Defines the name of the search parameter. | | :apiHeaders | Inside data-hs-combo-box | string | null | null | Defines request headers. | | :apiSearchPath | Inside data-hs-combo-box | string | null | null | A string that specifies the endpoint path for the API request, excluding the base URL. Note: apiSearchPath and apiSearchDefaultPath are mutually exclusive with apiSearchQuery. | | :apiSearchDefaultPath | Inside data-hs-combo-box | string | null | null | A string that defines the default API endpoint path to be used when the input field is empty. Note: apiSearchPath and apiSearchDefaultPath are mutually exclusive with apiSearchQuery. | | :outputItemTemplate | Inside data-hs-combo-box | string | null | Default template | Defines a template for a single item in a dropdown list. | | :outputEmptyTemplate | Inside data-hs-combo-box | string | null | Default template | Defines a template for an empty placeholder. | | :outputLoaderTemplate | Inside data-hs-combo-box | string | null | Default template | Defines a template for the loader when loading data. | | :preventAutoPosition | Inside data-hs-combo-box | boolean | false | If true, it disables dropdown auto-positioning. | | :preventClientFiltering | Inside data-hs-combo-box | boolean | true (if :apiSearchQuery is not empty) | If true, it disables client-side filtering. | | :keepOriginalOrder | Inside data-hs-combo-box | boolean | false | If true, it keeps the original order of items. | | :preserveSelectionOnEmpty | Inside data-hs-combo-box | boolean | true | If true, it preserves the selected value when the input is empty. | | data-hs-combo-box-input | Input element | - | - | Determines which element (input) inside the initialized container will be responsible for entering data. | | data-hs-combo-box-output | Output container | - | - | Determines which element inside the initialized container will be responsible for data output. | | data-hs-combo-box-toggle | Toggle element | - | - | Defines an element inside the initialized container that will be responsible for hiding/showing the dropdown list. | | data-hs-combo-box-close | Close element | - | - | Defines an element inside the initialized container that will be responsible for hiding the dropdown list. | | data-hs-combo-box-open | Open element | - | - | Defines an element inside the initialized container that will be responsible for showing the dropdown list. | | data-hs-combo-box-output-item | Item element | - | - | Defines an element inside the initialized container that will be responsible for displaying each individual data element. | | data-hs-combo-box-search-text | Search text element | - | - | Defines the element within which text will be searched. | | data-hs-combo-box-value | Value element | - | - | Defines an element whose text will be set as a value when selected. | | data-hs-combo-box-output-item-field | Item field | string | string[] | - | Defines a data field that will be taken to fill the element with text. | | data-hs-combo-box-output-item-attr | Item attribute | - | - | Defines the attributes that will be filled with the corresponding data. For example, the src attribute of an image. | | :valueFrom | Inside data-hs-combo-box-output-item-attr | string | - | Defines the name of the field from which data will be taken. | | :attr | Inside data-hs-combo-box-output-item-attr | string | - | Defines the name of the attribute where the data will be supplied. |

Tailwind Modifiers

| Name | Description | | --- | --- | | hs-combo-box-active:* | A modifier that allows you to set Tailwind classes when ComboBox has been opened. | | hs-combo-box-has-value:* | A modifier that allows you to set Tailwind classes when ComboBox's input has value. | | hs-combo-box-selected:* | A modifier that allows you to set Tailwind classes when data-hs-combo-box-output-item has been selected. | | hs-combo-box-tab-active:* | A modifier that allows you to set Tailwind classes to the active group item (tab) when groupingType is tabs. |

JavaScript API

The HSComboBox object is available in the global window object after the plugin is loaded.

Instance Methods

These methods are called on a combobox instance.

| Method | Parameters | Return Type | Description | | --- | --- | --- | --- | | getCurrentData() | None | object \| object[] | Returns the data of the selected element as an object. This data must first be assigned as a value to the data parameter data-hs-combo-box-item-stored-data when standard rendering. When rendering via the API, the data is automatically substituted into the data attribute. | | setCurrent() | None | void | Sets the current selection based on the input value. | | open(val) | val: string (optional) | boolean | Opens the autosuggestion list. Optionally accepts a value to set in the input. Returns true if opened successfully, false otherwise. | | close(val, data) | val: string \| null (optional)data: object \| null (optional) | boolean | Closes the autosuggestion list. Optionally accepts a value and data to set. Returns true if closed successfully, false otherwise. | | recalculateDirection() | None | void | Forces recalculation of autosuggestion list positions. Useful after window resize or layout changes. | | destroy() | None | void | Destroys the combobox instance, removes all generated markup, classes, and event listeners. Use when removing combobox from DOM. |

Static Methods

These methods are called directly on the HSComboBox class.

| Method | Parameters | Return Type | Description | | --- | --- | --- | --- | | HSComboBox.getInstance(target, isInstance) | target: HTMLElement \| string (CSS selector)isInstance: boolean (optional) | HSComboBox \| { id: string \| number, element: HSComboBox } \| null | Returns the combobox instance associated with the target. If isInstance is true, returns collection item object { id, element } where element is the HSComboBox instance. If isInstance is false or omitted, returns the HSComboBox instance directly. Returns null if combobox instance is not found. | | HSComboBox.autoInit() | None | void | Reinitializes all ComboBoxes on the page. Useful after dynamically adding comboboxes to DOM. | | HSComboBox.close(target) | target: HTMLElement \| string (CSS selector) | void | Closes the combobox identified by target. Accepts a DOM element or CSS selector string. | | HSComboBox.closeCurrentlyOpened() | None | void | Closes an already open ComboBox. Useful for closing any open combobox before opening a new one. |

Usage Examples

Example 1: Using instance methods (public API)

// Create a new combobox instance
const comboBox = new HSComboBox(document.querySelector('#hs-combo-box'));
const openBtn = document.querySelector('#hs-open-btn');

// Open combobox programmatically
openBtn.addEventListener('click', () => {
  comboBox.open();
});

Example 2: Getting instance and using methods (recommended pattern)

// Get the combobox instance
const instance = HSComboBox.getInstance('#hs-combo-box', true);

if (instance) {
  const { element } = instance; // element is the HSComboBox instance
  const openBtn = document.querySelector('#hs-open-btn');

  // Use instance methods
  openBtn.addEventListener('click', () => {
    element.open();
  });

  // Get selected data
  const selectedData = element.getCurrentData();
  console.log('Selected:', selectedData);

  // Clean up when removing from DOM
  function removeComboBox() {
    element.destroy();
  }
}

Example 3: Destroying combobox instance

const instance = HSComboBox.getInstance('#hs-combo-box', true);

if (instance) {
  const { element } = instance;
  const removeBtn = document.querySelector('#hs-remove-btn');

  removeBtn.addEventListener('click', () => {
    // Clean up before removing from DOM
    element.destroy();
    // Now safe to remove the element
    document.querySelector('#hs-combo-box').remove();
  });
}

Events

Combobox instances emit events that can be listened to for selection lifecycle hooks.

| Event Name | When Fired | Callback Parameter | Description | | --- | --- | --- | --- | | on:select | When an item is selected from the dropdown | object (the selected item data object) | Fires after the user clicks an option in the combobox dropdown. |

Event Usage Example

// Get combobox instance
const instance = HSCombobox.getInstance('#hs-combobox', true);

if (instance) {
  const { element } = instance;

  // Listen for item selection
  element.on('select', (data) => {
    console.log('Selected item:', data);
    // Use selected data to update other parts of the UI
  });
}

Common Patterns

Pattern 1: API-based ComboBox

Fetch suggestions from an API endpoint.

<div data-hs-combo-box='{
  "apiUrl": "https://api.example.com/search",
  "apiSearchQuery": "q",
  "minSearchLength": 2
}'>
  <input data-hs-combo-box-input />
  <div data-hs-combo-box-output></div>
</div>

Pattern 2: Programmatic Control

Control combobox from external buttons.

<div id="hs-combo-box-first" data-hs-combo-box>
  <input data-hs-combo-box-input />
  <div data-hs-combo-box-output></div>
</div>

<button id="hs-open-combo-box">Open</button>
<button id="hs-close-combo-box">Close</button>

<script>
  const instance = HSComboBox.getInstance('#hs-combo-box-first', true);
  
  if (instance) {
    const { element } = instance;

    document.querySelector('#hs-open-combo-box').addEventListener('click', () => {
      element.open();
    });

    document.querySelector('#hs-close-combo-box').addEventListener('click', () => {
      element.close();
    });
  }
</script>

License

Copyright (c) 2026 Preline Labs.

Licensed under the MIT License.