Data and type casting

Karl53

DataTables 1.10.5. Editor 1.4 Using inline editing.

I'm familiar with what is written here data.

While I have things working for the most part, I seem to be fighting my data and probably doing some unnecessary type casting.

My question is therefore about best practices around how to best work with data types, particularly JavaScript numbers and Date objects. For example, I have a column that shows the row number and as rows are inserted or deleted, the row number is dynamically update. Sometimes the row number value, rather than being an number is a string.

Do I understand what is happening? My adjax function, originally looked like this:

    "ajax": function (method, url, data, success, error) {
        var obj = {};
        if (data.action === 'edit') {
            success({row: data.data});
        }
    },

1. But I gather that since data.data is a jason object, the values of the object will always be strings. Correct? The server certainly isn't going to know what a JavaScript Data object is. Or am I misinterpreting what I'm seeing and I have bugs somewhere in my program due to type casting my code might be doing?

To minimize type casting I've started to change my data handling to following this pattern:

    "ajax": function (method, url, data, success, error) {
        var obj = {};
        if (data.action === 'edit') {
            obj = { "idx" : parseInt(data.data.idx, 10),
                    "rowNum" :  parseInt(data.data.rowNum, 10),
                    "myDate" : data.data.myDate,
                    "myColor" : data.data.myColor,
                    "nSalesDays" : data.data.nSalesDays,
                    "myEndDate" : data.data.myEndDate,
            success(obj);
        }
    },

2. Am I on the right track? Or maybe the objects managed by DataTable's Data array should all be fields that are string type? Using this technique I would then have to type cast at the point in the code where performing date or integer math.

3. Here's a Render function. In the if (type === 'display'), the return, is the result only changing what is being displayed, or is the underlying value being impacted as well? Could use a little clarity as to what I maybe should and should not do in render.

    {"data": 'myEndDate', "width": "10%", "defaultContent": null, "orderable": false, "render": function (data, type, row, meta) {
        if (typeof data === "string" && data !== '') {
            data = dateToFormat(data);
        }
        // 'display', 'sort', 'filter', 'type'
        if (type === 'display' && data !== null && data !== '') {
            return toCustomDateString(data);
        }
        return data;
    }},

Any pointers on what is considered best practices for working with data types would be appreciated.

Thank you.

allan

1) But I gather that since data.data is a jason object, the values of the object will always be strings. Correct?

No. JSON can contain numbers, strings, objects, arrays, null and boolean values. However, if you submit the data to the server, then by default Editor will use HTTP variables to represent the data. These are plain text and so any type may be lost. Most server-side frameworks will automatically attempt to detect the type and convert it (PHP for example does this).

The server certainly isn't going to know what a JavaScript Data object is.

Correct - JSON cannot represent complex objects like Date. For that you need to use a string representation of the date and then convert it back on the server-side.

The other thing to be aware of is that when a value is read from an <input> field, it is read as a string. Again there is no type information. That would explain why you are currently using parseInt for your rowNum input.

2) Am I on the right track?

In this case, yes I would say so since you are not using a server-side database. I would point out however that the obj you are returning to success does not conform to what Editor expects. Specifically the row parameter is missing.

My suggestion would be that the callbacks / events you are using for Editor should ensure that DataTables always sees the same type for each data point. i.e. if rowNum is a number on load, it should always be a number.

Or maybe the objects managed by DataTable's Data array should all be fields that are string type?

Could you clarify what you mean by "DataTable's Data array"? DataTables will just hold whatever information you give it for each row.

3) Here's a Render function. In the if (type === 'display'), the return, is the result only changing what is being displayed, or is the underlying value being impacted as well?

The whole point of the columns.render option is that the underlying data is not modified in order to present formatted data to DataTables. The old fnRender method that columns.render replaced did write to the data source object and it was a compatibility and performance nightmare. It was dropped in 1.10 as it wouldn't have been possible to do much of what 1.10 does with it!

What you have looks okay, but again I would suggest you are consistent with the data given to DataTables. If it is a Date object then it should always expect a Date object and anything else is a bug. That might require type casting in an event handler as discussed above, to a large extent it depends upon what the date input type you are using does! Some will happily give you a Date object, some ISO8601 always, etc.

Regards,
Allan