Core: .each/.map should accept an undefined/null value

(cherry-picked from bf48c21)

Fixes gh-2267
Closes gh-2363

src/core.js

@@ -294,11 +294,10 @@ jQuery.extend({
 	},
 
 	each: function( obj, callback ) {
-		var i = 0,
-			length = obj.length,
-			isArray = isArraylike( obj );
+		var length, i = 0;
 
-		if ( isArray ) {
+		if ( isArrayLike( obj ) ) {
+			length = obj.length;
 			for ( ; i < length; i++ ) {
 				if ( callback.call( obj[ i ], i, obj[ i ] ) === false ) {
 					break;
@@ -327,7 +326,7 @@ jQuery.extend({
 		var ret = results || [];
 
 		if ( arr != null ) {
-			if ( isArraylike( Object(arr) ) ) {
+			if ( isArrayLike( Object( arr ) ) ) {
 				jQuery.merge( ret,
 					typeof arr === "string" ?
 					[ arr ] : arr
@@ -405,14 +404,13 @@ jQuery.extend({
 
 	// arg is for internal usage only
 	map: function( elems, callback, arg ) {
-		var value,
+		var length, value,
 			i = 0,
-			length = elems.length,
-			isArray = isArraylike( elems ),
 			ret = [];
 
 		// Go through the array, translating each of the items to their new values
-		if ( isArray ) {
+		if ( isArrayLike( elems ) ) {
+			length = elems.length;
 			for ( ; i < length; i++ ) {
 				value = callback( elems[ i ], i, arg );
 
@@ -493,13 +491,13 @@ function(i, name) {
 	class2type[ "[object " + name + "]" ] = name.toLowerCase();
 });
 
-function isArraylike( obj ) {
+function isArrayLike( obj ) {
 
 	// Support: iOS 8.2 (not reproducible in simulator)
 	// `in` check used to prevent JIT error (gh-2145)
 	// hasOwn isn't used here due to false negatives
 	// regarding Nodelist length in IE
-	var length = "length" in obj && obj.length,
+	var length = !!obj && "length" in obj && obj.length,
 		type = jQuery.type( obj );
 
 	if ( type === "function" || jQuery.isWindow( obj ) ) {

test/unit/core.js

@@ -1182,6 +1182,18 @@ test("jQuery.each(Object,Function)", function() {
 	equal( i, document.styleSheets.length, "Iteration over document.styleSheets" );
 });
 
+test("jQuery.each/map(undefined/null,Function)", 1, function() {
+	try {
+		jQuery.each( undefined, jQuery.noop );
+		jQuery.each( null, jQuery.noop );
+		jQuery.map( undefined, jQuery.noop );
+		jQuery.map( null, jQuery.noop );
+		ok( true, "jQuery.each/map( undefined/null, function() {} );" );
+	} catch ( e ) {
+		ok( false, "each/map must accept null and undefined values" );
+	}
+});
+
 test( "JIT compilation does not interfere with length retrieval (gh-2145)", function() {
 	expect( 4 );