Aleyna Aleyna - 2 months ago 13
JSON Question

How to use JSON.parse reviver parameter to parse date string

My JSON string contains a date field that returns such a value:

"2009-04-04T22:55:16.0000000-04:00"


I am particularly interested in parsing only the date compartment not the time. I tried using a reviver function, but interestingly the reviver function is never invoked! (tried on Firefox)

Here is my code to accomplish that:

var Site = {
.....
dateReviver: function(key, value) {
var a;
if (typeof value === 'string') {
a = /^(\d{4})-(\d{2})-(\d{2})T(\d{2}):(\d{2}):(\d{2}(?:\.\d*)?)Z$/.exec(value);
if (a) {
return new Date(Date.UTC(+a[1], +a[2] - 1, +a[3], +a[4],
+a[5], +a[6]));
}
}
return value;
},
loadArticle: function(id) {
....
proxy.getArticle(id, function(response) {
var data = JSON.parse(response.result, Site.dateReviver);
....
});
}
};


JSON.parse in
loadArticle
never calls
dateReviver
.

I invested a whole day but no luck! Could someone please help me?

Answer
  1. The regular expression expects a "Zulu" timezone (A 'Z' character at the end), while the sample date-time string shows a numeric timezone ('-04:00'). The following regex will accept both:

    /^(\d{4})-(\d{2})-(\d{2})T(\d{2}):(\d{2}):(\d{2}(?:\.\d*)?)(Z|([+\-])(\d{2}):(\d{2}))$/
    

    If the time zone digits are not zero, you might want to actually modify the date after parsing and/or converting to UTC, to respect the timezone.

  2. I can see dateReviver() being hit. Try the following in a browser:

    <!-- saved from url=(0014)about:internet -->
    <html>
        <head>
            <script src="http://www.json.org/json2.js"></script>
            <script type="text/javascript" src="http://ajax.Microsoft.com/ajax/jQuery/jquery-1.3.2.js"></script>
            <script>
                $(function () {
                    // a mock proxy to return some json to play with
                    var proxy = {
                        getArticle: function(id, foo) { foo({
                            result: '["2009-04-04T22:55:16.0000000-04:00"]'
                        }); }
                    };
                    // the origial Site object, with the fixed regex
                    var Site = {
                        dateReviver: function(key, value) {
                            var a;
                            if (typeof value === 'string') {
                                a = /^(\d{4})-(\d{2})-(\d{2})T(\d{2}):(\d{2}):(\d{2}(?:\.\d*)?)(Z|([+\-])(\d{2}):(\d{2}))$/.exec(value);
                                if (a) {
                                    return new Date(Date.UTC(+a[1], +a[2] - 1, +a[3], +a[4],
                                                    +a[5], +a[6]));
                                }
                            }
                            return value;
                        },
                        loadArticle: function(id) {
                            proxy.getArticle(id, function(response) {
                                var data = JSON.parse(response.result, Site.dateReviver);
                                // put the parsed JSON date on the page
                                $("#output").html(data[0].toString());
                            });
                        }
                    };
                    // try out our Site object
                    Site.loadArticle();
                });
            </script>
        </head>
        <body>
            <div id="output"></div>
        </body>
    </html>
    

    I am getting the following in the browser, indicating successful parsing:

    Sat Apr 4 15:55:16 PDT 2009
    
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