jquery.fileupload-image-editor.js中

  _initEventHandlers: function () {
            this._super();

            var handlers = {};
            handlers[this.options.uploadImageEditorPreviewSelector] = this._previewHandler.bind(this);

            this._on(this.options.filesContainer, handlers);
        },

 

jquery.ui.widget.js

    _on: function( suppressDisabledCheck, element, handlers ) {
        var delegateElement,
            instance = this;

        // no suppressDisabledCheck flag, shuffle arguments
        if ( typeof suppressDisabledCheck !== "boolean" ) {
            handlers = element;
            element = suppressDisabledCheck;
            suppressDisabledCheck = false;
        }

        // no element argument, shuffle and use this.element
        if ( !handlers ) {
            handlers = element;
            element = this.element;
            delegateElement = this.widget();
        } else {
            element = delegateElement = $( element );
            this.bindings = this.bindings.add( element );
        }

https://api.jqueryui.com/jQuery.widget/#method-_on

_on( [suppressDisabledCheck ] [, element ], handlers )Returns: jQuery (plugin only)

Binds event handlers to the specified element(s). Delegation is supported via selectors inside the event names, e.g., "click .foo". The _on() method provides several benefits of direct event binding:

• Maintains proper this context inside the handlers.
• Automatically handles disabled widgets: If the widget is disabled or the event occurs on an element with the ui-state-disabled class, the event handler is not invoked. Can be overridden with the suppressDisabledCheck parameter.
• Event handlers are automatically namespaced and cleaned up on destroy.

• suppressDisabledCheck (default: false) Type: Boolean Whether or not to bypass the disabled check.
• element Type: jQuery Which element(s) to bind the event handlers to. If no element is provided, this.element is used for non-delegated events and the widget element is used for delegated events.
• handlers Type: Object An object in which the keys represent the event type and optional selector for delegation, and the values represent a handler function to be called for the event.

Code examples:

Prevent the default action of all links clicked within the widget's element.

this._on( this.element, {
  "click a": function( event ) {
    event.preventDefault();
  }
});