Support dates

README.md

@@ -1,7 +1,7 @@
 Serialize JavaScript
 ====================
 
-Serialize JavaScript to a _superset_ of JSON that includes regular expressions and functions.
+Serialize JavaScript to a _superset_ of JSON that includes regular expressions, dates and functions.
 
 [![npm Version][npm-badge]][npm]
 [![Dependency Status][david-badge]][david]
@@ -11,7 +11,7 @@ Serialize JavaScript to a _superset_ of JSON that includes regular expressions a
 
 The code in this package began its life as an internal module to [express-state][]. To expand its usefulness, it now lives as `serialize-javascript` — an independent package on npm.
 
-You're probably wondering: **What about `JSON.stringify()`!?** We've found that sometimes we need to serialize JavaScript **functions** and **regexps**. A great example is a web app that uses client-side URL routing where the route definitions are regexps that need to be shared from the server to the client.
+You're probably wondering: **What about `JSON.stringify()`!?** We've found that sometimes we need to serialize JavaScript **functions**, **regexps** or **dates**. A great example is a web app that uses client-side URL routing where the route definitions are regexps that need to be shared from the server to the client.
 
 The string returned from this package's single export function is literal JavaScript which can be saved to a `.js` file, or be embedded into an HTML document by making the content of a `<script>` element. **HTML charaters and JavaScript line terminators are escaped automatically.**
 
@@ -36,6 +36,7 @@ serialize({
     bool : true,
     nil  : null,
     undef: undefined,
+    date: new Date("Thu, 28 Apr 2016 22:02:17 GMT"),
 
     fn: function echo(arg) { return arg; },
     re: /([^\s]+)/g
@@ -45,7 +46,7 @@ serialize({
 The above will produce the following string output:
 
 ```js
-'{"str":"string","num":0,"obj":{"foo":"foo"},"arr":[1,2,3],"bool":true,"nil":null,"fn":function echo(arg) { return arg; },"re":/([^\\s]+)/g}'
+'{"str":"string","num":0,"obj":{"foo":"foo"},"arr":[1,2,3],"bool":true,"nil":null,date:new Date("2016-04-28T22:02:17.156Z"),"fn":function echo(arg) { return arg; },"re":/([^\\s]+)/g}'
 ```
 
 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

@@ -10,7 +10,7 @@ var isRegExp = require('util').isRegExp;
 
 // Generate an internal UID to make the regexp pattern harder to guess.
 var UID                 = Math.floor(Math.random() * 0x10000000000).toString(16);
-var PLACE_HOLDER_REGEXP = new RegExp('"@__(FUNCTION|REGEXP)-' + UID + '-(\\d+)__@"', 'g');
+var PLACE_HOLDER_REGEXP = new RegExp('"@__(FUNCTION|REGEXP|DATE)-' + UID + '-(\\d+)__@"', 'g');
 
 var IS_NATIVE_CODE_REGEXP = /\{\s*\[native code\]\s*\}/g;
 var UNSAFE_CHARS_REGEXP   = /[<>\/\u2028\u2029]/g;
@@ -25,13 +25,31 @@ var UNICODE_CHARS = {
     '\u2029': '\\u2029'
 };
 
+// We can‘t just instanceof Date since dates are already converted to strings
+// because of native Date.prototype.JSON (which use toISOString)
+var DATE_LENGTH = new Date().toISOString().length
+function isDate(d) {
+  try {
+    return (
+      // testing length first to avoid new Date() for every string
+      d.length === DATE_LENGTH &&
+      d === ((new Date(d)).toISOString())
+    )
+  }
+  // Invalid Date might throw "RangeError: invalid date" when calling toISOString
+  catch(e) {}
+
+  return false
+}
+
 module.exports = function serialize(obj, space) {
     var functions = [];
     var regexps   = [];
+    var dates   = [];
     var str;
 
     // Creates a JSON string representation of the object and uses placeholders
-    // for functions and regexps (identified by index) which are later
+    // for functions, regexps and dates (identified by index) which are later
     // replaced.
     str = JSON.stringify(obj, function (key, value) {
         if (typeof value === 'function') {
@@ -42,6 +60,10 @@ module.exports = function serialize(obj, space) {
             return '@__REGEXP-' + UID + '-' + (regexps.push(value) - 1) + '__@';
         }
 
+        if (typeof value === 'string' && isDate(value)) {
+            return '@__DATE-' + UID + '-' + (dates.push(value) - 1) + '__@';
+        }
+
         return value;
     }, space);
 
@@ -58,14 +80,22 @@ module.exports = function serialize(obj, space) {
         return UNICODE_CHARS[unsafeChar];
     });
 
-    if (functions.length === 0 && regexps.length === 0) {
+    if (
+      functions.length === 0 &&
+      regexps.length === 0 &&
+      dates.length === 0
+    ) {
         return str;
     }
 
-    // Replaces all occurrences of function and regexp placeholders in the JSON
-    // string with their string representations. If the original value can not
-    // be found, then `undefined` is used.
+    // Replaces all occurrences of function, regexp and date placeholders in the
+    // JSON string with their string representations.
+    // If the original value can not be found, then `undefined` is used.
     return str.replace(PLACE_HOLDER_REGEXP, function (match, type, valueIndex) {
+        if (type === 'DATE') {
+            return "new Date(\"" + dates[valueIndex] + "\")";
+        }
+
         if (type === 'REGEXP') {
             return regexps[valueIndex].toString();
         }

package.json

@@ -1,7 +1,7 @@
 {
   "name": "serialize-javascript",
   "version": "1.2.0",
-  "description": "Serialize JavaScript to a superset of JSON that includes regular expressions and functions.",
+  "description": "Serialize JavaScript to a superset of JSON that includes regular expressions, dates and functions.",
   "main": "index.js",
   "scripts": {
     "benchmark": "node test/benchmark/serialize.js",

test/unit/serialize.js

@@ -169,4 +169,23 @@ describe('serialize( obj )', function () {
             expect(eval(serialize('</script>'))).to.equal('</script>');
         });
     });
+
+    describe('dates', function () {
+        it('should serialize dates', function () {
+            var d = new Date('2016-04-28T22:02:17.156Z');
+            expect(serialize(d)).to.be.a('string').equal('new Date("2016-04-28T22:02:17.156Z")');
+        });
+
+        it('should deserialize a date', function () {
+            var d = eval(serialize(new Date('2016-04-28T22:02:17.156Z')));
+            expect(d).to.be.a('Date');
+            expect(d.toISOString()).to.equal('2016-04-28T22:02:17.156Z');
+        });
+
+        it('should deserialize a string that is not a valid date', function () {
+            var d = eval(serialize('2016-04-28T25:02:17.156Z'));
+            expect(d).to.be.a('string');
+            expect(d).to.equal('2016-04-28T25:02:17.156Z');
+        });
+    })
 });