I'd like to try FFI with JS.
For that purpose, I'd like to play with
[crossfilter](https://github.com/crossfilter/crossfilter).
A minimal crossfilter example looks like `example.js`:
var livingThings = crossfilter([
// Fact data.
{ name: "Rusty", type: "human", legs: 2 },
{ name: "Alex", type: "human", legs: 2 },
{ name: "Lassie", type: "dog", legs: 4 },
{ name: "Spot", type: "dog", legs: 4 },
{ name: "Polly", type: "bird", legs: 2 },
{ name: "Fiona", type: "plant", legs: 0 }
]);
// How many living things are in my house?
var n = livingThings.groupAll().reduceCount().value();
console.log("There are " + n + " living things in my house.") // 6
Run
With `index.html`:
<html>
<body>
<script type="text/javascript" src="crossfilter.min.js"></script>
<script type="text/javascript" src="example.js"></script>
</body>
</html>
Run
I don't know how should I send the data to the JavaScript function. I tried
something like the following for the FFI part:
import json
when not defined(js):
{.error: "This module only works on the JavaScript platform".}
type
Crossfilter = ref object
proc crossfilter*(a:JsonNode): Crossfilter {.importc:"crossfilter".}
proc groupAll*(a:Crossfilter):Crossfilter {.importc:"crossfilter.groupAll".}
proc reduceCount*(a:Crossfilter):Crossfilter
{.importc:"crossfilter.reduceCount".}
proc value*(a:Crossfilter):int {.importc:"crossfilter.value".}
Run
and the following for the Nim replacement code:
import crossfilter, json
let data = """
[
{ name: "Rusty", type: "human", legs: 2 },
{ name: "Alex", type: "human", legs: 2 },
{ name: "Lassie", type: "dog", legs: 4 },
{ name: "Spot", type: "dog", legs: 4 },
{ name: "Polly", type: "bird", legs: 2 },
{ name: "Fiona", type: "plant", legs: 0 }
]
"""
let livingThings = crossfilter(data.parseJson)
var n = livingThings.groupAll().reduceCount().value()
echo "There are " & $n & " living things in my house."
Run
How should I send `data` to `crossfilter`?
