How do I chain "SelectMany" calls with linqjs (or flatten JSON)

javascript, linq, linq.js

Solution

You don't need to really chain anything. Your root object is an array, you just want to select each widget for each object in that array.

var query = Enumerable.From(jsonObject)
    .SelectMany("$.Widgets") // Select each widget found in the Widgets property
    .ToArray();

To flatten that array of widgets attaching each property of the parent object to the result, there's a couple of ways you could do it. You can use a nested query using the function syntax.

var query = Enumerable.From(jsonObject)
    .SelectMany(function (item) {
        return Enumerable.From(item.Widgets)
            .Select(function (widget) {
                return {
                    ID: widget.ID,
                    Name: widget.Name,
                    UpFrontCost: item.UpFrontCost,
                    Currency: item.Currency,
                    FittingDate: item.FittingDate
                };
            });
    })
    .ToArray();

Or using the lambda string syntax:

var query = Enumerable.From(items)
    .SelectMany("$.Widgets",
        // argument 1 ($) - the parent object
        // argument 2 ($$) - the selected object (a widget)
        "{ ID: $$.ID, Name: $$.Name, UpFrontCost: $.UpFrontCost, Currency: $.Currency, FittingDate: $.FittingDate }"
    )
    .ToArray();

Problem

Using linq.js how can I chain two SelectMany calls together. Given the following JSON structure: ``` [ { "UpFrontCost": "29.95", "Currency": "USDAUD", "FittingDate": "2013-07-08 06:30:16Z", "Widgets": [ { "ID": 3, "Name": "Test1" }, { "ID": 4, "Name": "Test19" }, { "ID": 6, "Name": "Test8" } ] }, { "UpFrontCost": "29.95", "Currency": "USDAUD", "FittingDate": "2013-07-08 06:30:16Z", "Widgets": [ { "ID": 67, "Name": "Test1" }, { "ID": 99, "Name": "Test19" }, { "ID": 34, "Name": "Test8" } ] } ] ``` I would like a list of all the "Widgets" (in this example a list of 6 widgets).

Original source