Accordion: Rewrite all :even usage to .even()

The polyfill for `.even()` & `.odd()` is added for jQuery <3.5.0.

There was no usage of the :odd selector in the code but the `.odd()` method
is also polyfilled for completeness.

Author: mgol

tests/lib/bootstrap.js

@@ -172,8 +172,11 @@ function migrateUrl() {
 		}
 	}
 
+	var jQueryVersion = parseUrl().jquery;
+
 	// Load the jQuery fixes, if necessary
-	if ( parseFloat( parseUrl().jquery ) < 3 ) {
+	if ( !jQueryVersion ||
+		( jQueryVersion.indexOf( "git" ) === -1 && parseFloat( jQueryVersion ) < 4 ) ) {
 		modules.unshift( "ui/jquery-1-7" );
 	}
 

tests/unit/accordion/common.js

@@ -15,7 +15,9 @@ common.testWidget( "accordion", {
 		collapsible: false,
 		disabled: false,
 		event: "click",
-		header: "> li > :first-child, > :not(li):even",
+		header: function( elem ) {
+			return elem.find( "> li > :first-child" ).add( elem.find( "> :not(li)" ).even() );
+		},
 		heightStyle: "auto",
 		icons: {
 			"activeHeader": "ui-icon-triangle-1-s",

tests/unit/accordion/options.js

@@ -376,15 +376,15 @@ QUnit.test( "{ event: custom }", function( assert ) {
 QUnit.test( "{ header: default }", function( assert ) {
 	assert.expect( 2 );
 
-	// Default: > li > :first-child,> :not(li):even
-	// > :not(li):even
+	// Default: elem.find( "> li > :first-child" ).add( elem.find( "> :not(li)" ).even() )
+	// elem.find( "> :not(li)" ).even()
 	state( assert, $( "#list1" ).accordion(), 1, 0, 0 );
 
 	// > li > :first-child
 	state( assert, $( "#navigation" ).accordion(), 1, 0, 0 );
 } );
 
-QUnit.test( "{ header: custom }", function( assert ) {
+QUnit.test( "{ header: customString }", function( assert ) {
 	assert.expect( 6 );
 	var element = $( "#navigationWrapper" ).accordion( {
 		header: "h2"
@@ -398,6 +398,22 @@ QUnit.test( "{ header: custom }", function( assert ) {
 	state( assert, element, 0, 0, 1 );
 } );
 
+QUnit.test( "{ header: customFunction }", function( assert ) {
+	assert.expect( 6 );
+	var element = $( "#navigationWrapper" ).accordion( {
+		header: function( elem ) {
+			return elem.find( "h2" );
+		}
+	} );
+	element.find( "h2" ).each( function() {
+		assert.hasClasses( this, "ui-accordion-header" );
+	} );
+	assert.equal( element.find( ".ui-accordion-header" ).length, 3 );
+	state( assert, element, 1, 0, 0 );
+	element.accordion( "option", "active", 2 );
+	state( assert, element, 0, 0, 1 );
+} );
+
 QUnit.test( "{ heightStyle: 'auto' }", function( assert ) {
 	assert.expect( 3 );
 	var element = $( "#navigation" ).accordion( { heightStyle: "auto" } );

ui/jquery-1-7.js

@@ -98,4 +98,21 @@ if ( !$.uniqueSort ) {
 	$.uniqueSort = $.unique;
 }
 
+// Support: jQuery 3.4.x or older
+// These methods have been defined in jQuery 3.5.0.
+if ( !$.fn.even || !$.fn.odd ) {
+	$.fn.extend( {
+		even: function() {
+			return this.filter( function( i ) {
+				return i % 2 === 0;
+			} );
+		},
+		odd: function() {
+			return this.filter( function( i ) {
+				return i % 2 === 1;
+			} );
+		}
+	} );
+}
+
 } ) );

ui/widgets/accordion.js

@@ -48,7 +48,9 @@ return $.widget( "ui.accordion", {
 		},
 		collapsible: false,
 		event: "click",
-		header: "> li > :first-child, > :not(li):even",
+		header: function( elem ) {
+			return elem.find( "> li > :first-child" ).add( elem.find( "> :not(li)" ).even() );
+		},
 		heightStyle: "auto",
 		icons: {
 			activeHeader: "ui-icon-triangle-1-s",
@@ -279,7 +281,11 @@ return $.widget( "ui.accordion", {
 		var prevHeaders = this.headers,
 			prevPanels = this.panels;
 
-		this.headers = this.element.find( this.options.header );
+		if ( typeof this.options.header === "function" ) {
+			this.headers = this.options.header( this.element );
+		} else {
+			this.headers = this.element.find( this.options.header );
+		}
 		this._addClass( this.headers, "ui-accordion-header ui-accordion-header-collapsed",
 			"ui-state-default" );