jQuery.map to iterate over objects with a .length property

src/core.js

@@ -704,33 +704,33 @@ jQuery.extend({
 		return ret;
 	},
 
-	// arg is for internal usage only
+		// arg is for internal usage only
 	map: function( elems, callback, arg ) {
-		var ret = [], value, i = 0,
-			length = elems.length,
-			// same object detection used in jQuery.each, not full-proof but very speedy.
-			isObj = length === undefined;
-
-			// the work for the loops - run elems[x] through callback
-			inLoop = function( key ) {
-			  value = callback( elems[ key ], key, arg );
-
+		var value, ret = [],
+					i = 0,		
+					length = elems.length,
+					// process .length if it's just an object member
+					isArray = length !== undefined && ( elems[ length - 1 ] || jQuery.isArray( elems ) );
+
+		// Go through the array, translating each of the items to their
+		// new value (or values).
+		if ( isArray ) {
+			for ( ; i < length; i++ ) {
+				value = callback( elems[ i ], i, arg );
+
 				if ( value != null ) {
 					ret[ ret.length ] = value;
 				}
 			}
 
-    // Go thorugh every key on the object
-		if ( isObj ) {
+		// Go thorugh every key on the object, 
+		} else {		
 			for ( key in elems ) {
-			  inLoop( key );
-			}
-
-		// Go through the array, translating each of the items to their
-		// new value (or values).
-		} else {			
-			for ( ; i < length; i++ ) {
-				inLoop( i );
+				value = callback( elems[ key ], key, arg );
+
+				if ( value != null ) {
+					ret[ ret.length ] = value;
+				}
 			}
 		}
 

test/unit/core.js

@@ -608,7 +608,7 @@ test("first()/last()", function() {
 });
 
 test("map()", function() {
-	expect(6);
+	expect(7);
 
 	same(
 		jQuery("#ap").map(function(){
@@ -630,26 +630,28 @@ test("map()", function() {
 	var keys = jQuery.map( {a:1,b:2}, function( v, k ){
 		return k;
 	});
-
 	equals( keys.join(""), "ab", "Map the keys from a hash to an array" );
 
 	var values = jQuery.map( {a:1,b:2}, function( v, k ){
 		return v;
 	});
-
 	equals( values.join(""), "12", "Map the values from a hash to an array" );
+
+	// object with length prop
+	var values = jQuery.map( {a:1,b:2, length:3}, function( v, k ){
+		return v;
+	});
+	equals( values.join(""), "123", "Map the values from a hash with a length property to an array" );
 
 	var scripts = document.getElementsByTagName("script");
 	var mapped = jQuery.map( scripts, function( v, k ){
 		return v;
 	});
-
 	equals( mapped.length, scripts.length, "Map an array(-like) to a hash" );
 
 	var flat = jQuery.map( Array(4), function( v, k ){
 		return k % 2 ? k : [k,k,k];//try mixing array and regular returns
 	});
-
 	equals( flat.join(""), "00012223", "try the new flatten technique(#2616)" );
 });