forms.js

formParent: function() {
		var parent;

		if ( this[ 0 ].form && typeof this[ 0 ].form !== "string" ) {
			return $( this[ 0 ].form );
		} else if ( !this[ 0 ].form ) {
			return;
		}

		// Support: IE8 only ( the rest of the method )
		// IE8 supports the form property, but not the form attribute, worse yet if you supply the
		// form attribute it overwrites the form property with the string. Other supported browsers
		// like all other IE's and Android 2.3 support the form attribute not at all or partially.
		// We don't care in those cases because they still always return an element. We are not
		// trying to fix the form attribute here, only deal with the prop supplying a string.
		// we don't use document on the first line because we need to support document fragments
		parent = ( this[ 0 ].style ?
				// element within the document
				this[ 0 ].ownerDocument :
				// element is window or document
				this[ 0 ].document || this[ 0 ] ).getElementByID( element.form );
		if ( parent ) {
			return $( parent );
		}
		parent = this.closest( "form" );
		if ( parent.length ) {
			return parent;
		}
		return;
	},
	_findLabel: function() {
		var ancestor, labelSelector, id,
			parent;

		// Check control.labels first
		if ( this.element[ 0 ].labels !== undefined && this.element[ 0 ].labels.length > 0 ) {
			this.label = $( this.element[ 0 ].labels[ 0 ] );
			return;
		}

		// Support: IE <= 11, FF <= 37, Android <=2.3 only
		// Above browsers do not support control.labels everything below is to support them
		// as well as document fragments control.labels does not work on document fragments anywhere
		parent = this.element.closest( "label" );

		// Check if the input has a parent thats a label
		if ( parent.length > 0 ) {
			this.label = parent;
			this.parentLabel = true;
			return;
		}

		// We don't search against the document in case the element
		// is disconnected from the DOM
		ancestor = this.element.parents().last();

		// Look for the label based on the id
		id = this.element.attr( "id" );
		if ( id ) {
			labelSelector = "label[for='" +
				this.element.attr( "id" ).replace( escapeId, "\\$1" ) + "']";
			this.label = ancestor.find( labelSelector );

			if ( !this.label.length ) {

				// The label was not found, make sure ancestors exist. If they do check their
				// siblings, if they dont check the elements siblings
				ancestor = ancestor.length ? ancestor.siblings() : this.element.siblings();

				// Check if any of the new set of ancestors is the label
				this.label = ancestor.filter( labelSelector );
				if ( !this.label.length ) {

					// Still not found look inside the ancestors for the label
					this.label = ancestor.find( labelSelector );
				}
			}
		}
		if ( !this.label || !this.label.length ) {
			$.error( "No label found for checkboxradio widget" );
		}
	},