Question

183

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

rated 0 times [ 187] [ 4] / answers: 1 / hits: 17726 / 15 Years ago, tue, november 24, 2009, 12:00:00

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?

Answers

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andrewb

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answered 15 Years ago marvinm · Accepted Answer

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.

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