Add support for Error object (yahoo#135)

Author: SidStraw

README.md

@@ -47,13 +47,14 @@ serialize({
     fn   : function echo(arg) { return arg; },
     re   : /([^\s]+)/g,
     big  : BigInt(10),
+    err  : new Error('Error message.'),
 });
 ```
 
 The above will produce the following string output:
 
 ```js
-'{"str":"string","num":0,"obj":{"foo":"foo"},"arr":[1,2,3],"bool":true,"nil":null,"undef":undefined,"inf":Infinity,"date":new Date("2016-04-28T22:02:17.000Z"),"map":new Map([["hello","world"]]),"set":new Set([123,456]),"fn":function echo(arg) { return arg; },"re":new RegExp("([^\\\\s]+)", "g"),"big":BigInt("10")}'
+'{"str":"string","num":0,"obj":{"foo":"foo"},"arr":[1,2,3],"bool":true,"nil":null,"undef":undefined,"inf":Infinity,"date":new Date("2016-04-28T22:02:17.000Z"),"map":new Map([["hello","world"]]),"set":new Set([123,456]),"fn":function echo(arg) { return arg; },"re":new RegExp("([^\\\\s]+)", "g"),"big":BigInt("10"),"err":new Error("Error message.")}'
 ```
 
 Note: to produced a beautified string, you can pass an optional second argument to `serialize()` to define the number of spaces to be used for the indentation.

index.js

@@ -11,7 +11,7 @@ var randomBytes = require('randombytes');
 // Generate an internal UID to make the regexp pattern harder to guess.
 var UID_LENGTH          = 16;
 var UID                 = generateUID();
-var PLACE_HOLDER_REGEXP = new RegExp('(\\\\)?"@__(F|R|D|M|S|A|U|I|B|L)-' + UID + '-(\\d+)__@"', 'g');
+var PLACE_HOLDER_REGEXP = new RegExp('(\\\\)?"@__(F|R|D|M|S|A|U|I|B|L|E)-' + UID + '-(\\d+)__@"', 'g');
 
 var IS_NATIVE_CODE_REGEXP = /\{\s*\[native code\]\s*\}/g;
 var IS_PURE_FUNCTION = /function.*?\(/;
@@ -73,6 +73,7 @@ module.exports = function serialize(obj, options) {
     var infinities= [];
     var bigInts = [];
     var urls = [];
+    var errors = [];
 
     // Returns placeholders for functions and regexps (identified by index)
     // which are later replaced by their string representation.
@@ -119,6 +120,10 @@ module.exports = function serialize(obj, options) {
             if(origValue instanceof URL) {
                 return '@__L-' + UID + '-' + (urls.push(origValue) - 1) + '__@';
             }
+
+            if(origValue instanceof Error) {
+                return '@__E-' + UID + '-' + (errors.push(origValue) - 1) + '__@';
+            }
         }
 
         if (type === 'function') {
@@ -210,7 +215,7 @@ module.exports = function serialize(obj, options) {
         str = str.replace(UNSAFE_CHARS_REGEXP, escapeUnsafeChars);
     }
 
-    if (functions.length === 0 && regexps.length === 0 && dates.length === 0 && maps.length === 0 && sets.length === 0 && arrays.length === 0 && undefs.length === 0 && infinities.length === 0 && bigInts.length === 0 && urls.length === 0) {
+    if (functions.length === 0 && regexps.length === 0 && dates.length === 0 && maps.length === 0 && sets.length === 0 && arrays.length === 0 && undefs.length === 0 && infinities.length === 0 && bigInts.length === 0 && urls.length === 0 && errors.length === 0) {
         return str;
     }
 
@@ -261,6 +266,10 @@ module.exports = function serialize(obj, options) {
             return "new URL(\"" + urls[valueIndex].toString() + "\")"; 
         }
 
+        if (type === 'E') {
+            return "new Error(\"" + errors[valueIndex].message + "\")"; 
+        }
+
         var fn = functions[valueIndex];
 
         return serializeFunc(fn);

test/unit/serialize.js

@@ -466,6 +466,20 @@ describe('serialize( obj )', function () {
         });
     });
 
+    describe('Error', function () {
+        it('should serialize Error', function () {
+            var e = new Error('Error message.')
+            expect(serialize(e)).to.equal('new Error("Error message.")');
+            expect(serialize({t: [e]})).to.be.a('string').equal('{"t":[new Error("Error message.")]}');
+        });
+
+        it('should deserialize Error', function () {
+            var d = eval(serialize(new Error('Error message.')));
+            expect(d).to.be.a('Error');
+            expect(d.message).to.equal('Error message.');
+        });
+    });
+
     describe('XSS', function () {
         it('should encode unsafe HTML chars to Unicode', function () {
             expect(serialize('</script>')).to.equal('"\\u003C\\u002Fscript\\u003E"');