Make sure that a parsererror is thrown whenever malformed JSON comes back from a server (so that the Ajax error handler is called). Makes it uniform across browsers that do and don't have JSON.parse support.

Author: jeresig

src/ajax.js

@@ -570,20 +570,26 @@ jQuery.extend({
 
 		// The filter can actually parse the response
 		if ( typeof data === "string" ) {
-			// If the type is "script", eval it in global context
-			if ( type === "script" || !type && ct.indexOf("javascript") >= 0 ) {
-				jQuery.globalEval( data );
-			}
-
 			// Get the JavaScript object, if JSON is used.
 			if ( type === "json" || !type && ct.indexOf("json") >= 0 ) {
 				// Try to use the native JSON parser first
 				if ( window.JSON && window.JSON.parse ) {
 					data = window.JSON.parse( data );
 
+				// Make sure the incoming data is actual JSON
+				// Logic borrowed from http://json.org/json2.js
+				} else if (/^[\],:{}\s]*$/.test(data.replace(/\\(?:["\\\/bfnrt]|u[0-9a-fA-F]{4})/g, "@")
+					.replace(/"[^"\\\n\r]*"|true|false|null|-?\d+(?:\.\d*)?(?:[eE][+\-]?\d+)?/g, "]")
+					.replace(/(?:^|:|,)(?:\s*\[)+/g, ""))) {
+						data = (new Function("return " + data))();
+
 				} else {
-					data = (new Function("return " + data))();
+					throw "JSON Syntax Error: " + data;
 				}
+
+			// If the type is "script", eval it in global context
+			} else if ( type === "script" || !type && ct.indexOf("javascript") >= 0 ) {
+				jQuery.globalEval( data );
 			}
 		}
 

test/data/badjson.js

@@ -0,0 +1 @@
+{bad: 1}

test/unit/ajax.js

@@ -341,13 +341,13 @@ test("jQuery.param()", function() {
 
 test("synchronous request", function() {
 	expect(1);
-	ok( /^{ "data"/.test( jQuery.ajax({url: url("data/json_obj.js"), async: false}).responseText ), "check returned text" );
+	ok( /^{ "data"/.test( jQuery.ajax({url: url("data/json_obj.js"), dataType: "text", async: false}).responseText ), "check returned text" );
 });
 
 test("synchronous request with callbacks", function() {
 	expect(2);
 	var result;
-	jQuery.ajax({url: url("data/json_obj.js"), async: false, success: function(data) { ok(true, "sucess callback executed"); result = data; } });
+	jQuery.ajax({url: url("data/json_obj.js"), async: false, dataType: "text", success: function(data) { ok(true, "sucess callback executed"); result = data; } });
 	ok( /^{ "data"/.test( result ), "check returned text" );
 });
 
@@ -821,6 +821,25 @@ test("jQuery.ajax() - script, Remote with scheme-less URL", function() {
 	});
 });
 
+test("jQuery.ajax() - malformed JSON", function() {
+	expect(1);
+
+	stop();
+
+	jQuery.ajax({
+		url: "data/badjson.js",
+		dataType: "json",
+		success: function(){
+			ok( false, "Success." );
+			start();
+		},
+		error: function(xhr, msg) {
+			equals( "parsererror", msg, "A parse error occurred." );
+	  		start();
+		}
+	});
+});
+
 test("jQuery.ajax() - script by content-type", function() {
 	expect(1);