Further modified jQuery 1.4 .param() method to serialize arrays containing non-scalar values. PHP and jQuery BBQ can both deserialize these structures, while rack (as of 1.0.0) cannot.

src/ajax.js

@@ -591,7 +591,10 @@ jQuery.extend({
 	// Serialize an array of form elements or a set of
 	// key/values into a query string
 	param: function( a ) {
+		
 		var s = [],
+			
+			// Set jQuery.param.traditional to true for jQuery <= 1.3.2 behavior.
 			param_traditional = jQuery.param.traditional;
 		
 		function add( key, value ){
@@ -600,8 +603,38 @@ jQuery.extend({
 			s[ s.length ] = encodeURIComponent(key) + '=' + encodeURIComponent(value);
 		}
 		
-		// If an array was passed in, assume that it is an array
+		// Recursively encode parameters from object.
-		// of form elements
+		function buildParams( prefix, obj ) {
+			
+			if ( jQuery.isArray(obj) ) {
+				// Serialize array item.
+				jQuery.each( obj, function(i,v){
+					if ( param_traditional ) {
+						add( prefix, v );
+					} else {
+						// If array item is non-scalar (array or object), encode its numeric
+						// index to resolve deserialization ambiguity issues. Note that rack
+						// (as of 1.0.0) can't currently deserialize nested arrays properly,
+						// and attempting to do so may cause a server error. Possible fixes
+						// are to modify rack's deserialization algorithm or to provide an
+						// option or flag to force array serialization to be shallow.
+						buildParams( prefix + "[" + ( typeof v === "object" || jQuery.isArray(v) ? i : "" ) + "]", v );
+					}
+				});
+				
+			} else if ( !param_traditional && typeof obj === "object" ) {
+				// Serialize object item.
+				jQuery.each( obj, function(k,v){
+					buildParams( prefix + "[" + k + "]", v );
+				});
+				
+			} else {
+				// Serialize scalar item.
+				add( prefix, obj );
+			}
+		}
+		
+		// If an array was passed in, assume that it is an array of form elements.
 		if ( jQuery.isArray(a) || a.jquery ) {
 			// Serialize the form elements
 			jQuery.each( a, function() {
@@ -609,35 +642,11 @@ jQuery.extend({
 			});
 			
 		} else {
-			// Encode parameters from object, recursively. If
+			// If jQuery.param.traditional is set, encode the "old" way (the way
-			// jQuery.param.traditional is set, encode the "old" way
+			// 1.3.2 or older did it), otherwise encode params recursively.
-			// (the way 1.3.2 or older did it)
+			jQuery.each( a, buildParams );
-			jQuery.each( a, function buildParams( prefix, obj ) {
-				
-				if ( jQuery.isArray(obj) ) {
-					jQuery.each( obj, function(i,v){
-						// Due to rails' limited request param syntax, numeric array
-						// indices are not supported. To avoid serialization ambiguity
-						// issues, serialized arrays can only contain scalar values. php
-						// does not have this issue, but we should go with the lowest
-						// common denominator
-						add( prefix + ( param_traditional ? "" : "[]" ), v );
-					});
-					
-				} else if ( typeof obj == "object" ) {
-					if ( param_traditional ) {
-						add( prefix, obj );
-						
-					} else {
-						jQuery.each( obj, function(k,v){
-							buildParams( prefix ? prefix + "[" + k + "]" : k, v );
-						});
-					}
-				} else {
-					add( prefix, obj );
-				}
-			});
 		}
+		
 		// Return the resulting serialization
 		return s.join("&").replace(r20, "+");
 	}

test/unit/ajax.js

@@ -251,7 +251,7 @@ test("serialize()", function() {
 });
 
 test("jQuery.param()", function() {
-	expect(13);
+	expect(15);
 	
   equals( jQuery.param.traditional, undefined, "traditional flag, undefined by default" );
   
@@ -271,7 +271,10 @@ test("jQuery.param()", function() {
 	equals( jQuery.param(params), "foo%5Bbar%5D=baz&foo%5Bbeep%5D=42&foo%5Bquux%5D=All+your+base+are+belong+to+us", "even more arrays" );
 	
 	params = { a:[1,2], b:{ c:3, d:[4,5], e:{ x:[6], y:7, z:[8,9] }, f:true, g:false, h:undefined }, i:[10,11], j:true, k:false, l:[undefined,0], m:"cowboy hat?" };
-	equals( jQuery.param(params), "a%5B%5D=1&a%5B%5D=2&b%5Bc%5D=3&b%5Bd%5D%5B%5D=4&b%5Bd%5D%5B%5D=5&b%5Be%5D%5Bx%5D%5B%5D=6&b%5Be%5D%5By%5D=7&b%5Be%5D%5Bz%5D%5B%5D=8&b%5Be%5D%5Bz%5D%5B%5D=9&b%5Bf%5D=true&b%5Bg%5D=false&b%5Bh%5D=undefined&i%5B%5D=10&i%5B%5D=11&j=true&k=false&l%5B%5D=undefined&l%5B%5D=0&m=cowboy+hat%3F", "huge structure" );
+	equals( decodeURIComponent( jQuery.param(params) ), "a[]=1&a[]=2&b[c]=3&b[d][]=4&b[d][]=5&b[e][x][]=6&b[e][y]=7&b[e][z][]=8&b[e][z][]=9&b[f]=true&b[g]=false&b[h]=undefined&i[]=10&i[]=11&j=true&k=false&l[]=undefined&l[]=0&m=cowboy+hat?", "huge structure" );
+	
+	params = { a: [ 0, [ 1, 2 ], [ 3, [ 4, 5 ], [ 6 ] ], { b: [ 7, [ 8, 9 ], [ { c: 10, d: 11 } ], [ [ 12 ] ], [ [ [ 13 ] ] ], { e: { f: { g: [ 14, [ 15 ] ] } } }, 16 ] }, 17 ] };
+	equals( decodeURIComponent( jQuery.param(params) ), "a[]=0&a[1][]=1&a[1][]=2&a[2][]=3&a[2][1][]=4&a[2][1][]=5&a[2][2][]=6&a[3][b][]=7&a[3][b][1][]=8&a[3][b][1][]=9&a[3][b][2][0][c]=10&a[3][b][2][0][d]=11&a[3][b][3][0][]=12&a[3][b][4][0][0][]=13&a[3][b][5][e][f][g][]=14&a[3][b][5][e][f][g][1][]=15&a[3][b][]=16&a[]=17", "nested arrays" );
 	
 	jQuery.param.traditional = true;
 	
@@ -293,6 +296,9 @@ test("jQuery.param()", function() {
 	params = { a:[1,2], b:{ c:3, d:[4,5], e:{ x:[6], y:7, z:[8,9] }, f:true, g:false, h:undefined }, i:[10,11], j:true, k:false, l:[undefined,0], m:"cowboy hat?" };
 	equals( jQuery.param(params), "a=1&a=2&b=%5Bobject+Object%5D&i=10&i=11&j=true&k=false&l=undefined&l=0&m=cowboy+hat%3F", "huge structure" );
 	
+	params = { a: [ 0, [ 1, 2 ], [ 3, [ 4, 5 ], [ 6 ] ], { b: [ 7, [ 8, 9 ], [ { c: 10, d: 11 } ], [ [ 12 ] ], [ [ [ 13 ] ] ], { e: { f: { g: [ 14, [ 15 ] ] } } }, 16 ] }, 17 ] };
+	equals( jQuery.param(params), "a=0&a=1%2C2&a=3%2C4%2C5%2C6&a=%5Bobject+Object%5D&a=17", "nested arrays (not possible when jQuery.param.traditional == true)" );
+
 });
 
 test("synchronous request", function() {