jQuery UI _create Method in Widget Development

In jQuery UI widget development, the _create() method serves as the core constructor for a plugin instance. This article explains the primary purpose of _create(), its role within the jQuery UI Widget Factory lifecycle, how it differs from the _init() method, and the standard responsibilities developers delegate to it when building custom user interface components.

The Role of the _create() Method

The _create() method is automatically executed once when a widget is first instantiated on a DOM element. Its primary purpose is to perform one-time setup tasks required to initialize the widget's structure, state, and event bindings. Because it only fires during the initial instantiation, it guarantees that heavy setup logic does not execute redundantly during the widget's lifecycle.

Primary Responsibilities of _create()

When implementing _create(), developers typically handle tasks that modify the DOM or prepare internal states:

  • DOM Manipulation and Structuring: Modifying the target element (this.element), adding necessary wrapper elements, assigning CSS classes, and generating child elements required for the widget to render correctly.
  • Event Binding: Attaching event listeners using the widget factory's built-in this._on() method. Using this._on() ensures that handlers are scoped properly to the widget instance and can be automatically cleaned up when the widget is destroyed.
  • Internal State Initialization: Declaring internal properties, setting default internal values, and caching references to specific child DOM elements for performance optimization.
  • Reading Options: Accessing user-defined configurations passed via this.options to determine how the initial structure and attributes should be applied.

Code Example

$.widget("custom.myWidget", {
    options: {
        activeClass: "is-active",
        defaultText: "Click Me"
    },

    _create: function() {
        // Add styling classes
        this.element.addClass("custom-widget");

        // Create and append markup
        this.button = $("<button>")
            .text(this.options.defaultText)
            .appendTo(this.element);

        // Bind events using the widget helper
        this._on(this.button, {
            click: this._handleClick
        });
    },

    _handleClick: function(event) {
        this.element.toggleClass(this.options.activeClass);
    }
});

Difference Between _create() and _init()

A common point of confusion is the distinction between _create() and _init():

  • _create(): Executes strictly once during the initial widget creation. If a developer invokes the widget again on the same element (e.g., $(selector).myWidget()), _create() is skipped.
  • _init(): Executes after _create() on the initial run, and then re-runs on every subsequent call to the widget without arguments. It is intended for reset logic or re-evaluating state when the widget is invoked again.

Separating one-time DOM construction in _create() from repeatable state resets in _init() prevents duplicate event listeners and unnecessary DOM recreation.

Cleanup Considerations

Because _create() modifies the DOM and binds event handlers, any persistent alterations made here should have corresponding removal logic inside the _destroy() method. This ensures that when the widget instance is destroyed via .myWidget("destroy"), the DOM returns to its pre-widget state without leaving memory leaks or orphaned elements behind.