使用 Ramda 基于多个条件过滤列表

Question

I have a list of cars, that I want to filter based on a filter object, the cars:

const cars = [
    {original: {"make": "audi", "model": "a4"}},
    {original: {"make": "bmw", "model": "m5"}},
    {original: {"make": "mercedes", "model": "s"}},
    {original: {"make": "audi", "model": "a6"}},
];

The filter object, that can have multiple criteria for the same property (these should be considered as OR filters). Each entry in this dictionary ("make", "model") should be considered as an AND filter.

const filterObject = {
    "make": {
        filters: [
            {prop: "make", value: "audi"},
            {prop: "make", value: "bmw"}
        ]
    }, 
    "model": {
        filters: [
            {prop: "model", value: "a6"}
        ]
    }
}

So in this case I should get back the audi - a6 . With ramda I could get this far:

filter(
  where({
      make: equals("audi"),
      model: equals("a6")
  }), 
  map(x => x.original, data)
)

Which works, but there are a couple of problems:

1. filterObject is assembled dynamically, so I don't know beforehand what properties are filtered. I should somehow map the object inside where , but I got stuck with the multiple conditions criteria. How to make where be aware of multiple predicates for each property?
2. At the end I should get back the original (filtered) array. But the relevant part is hidden inside a property ( original ), so before I start filtering, I map over the array to supply the relevant part to the where function, therefore in the end this mapped array is returned.

Maybe where is not the right approach here?

Answer 1

R.where expects a an object with a predicate function for each property you wish to test. To pass a tested object needs to satisfy all predicates (and).

To test the current object's make lets say "audi` against an array of options (or), you can use R.includes.

So the first step is to create a where object, where each predicate checks the current object's value against an array of values.

 const { map, pipe, prop, pluck, includes, flip, where } = R; const createFilters = map(pipe( prop('filters'), pluck('value'), flip(includes) )); const cars = [{"original":{"make":"audi","model":"a4"}},{"original":{"make":"bmw","model":"m5"}},{"original":{"make":"mercedes","model":"s"}},{"original":{"make":"audi","model":"a6"}}]; const filterObject = {"make":{"filters":[{"prop":"make","value":"audi"},{"prop":"make","value":"bmw"}]},"model":{"filters":[{"prop":"model","value":"a6"}]}}; const filters = createFilters(filterObject); console.log(filters); console.log(where(filters, {"make":"audi","model":"a4"})) // false console.log(where(filters, {"make":"audi","model":"a6"})) // true

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Then you when filtering the data, get the object from the origin , and use the R.where with the applied filters:

 const { map, pipe, prop, pluck, includes, flip, curry, filter, where } = R; const createFilters = map(pipe( prop('filters'), pluck('value'), flip(includes) )); const fn = curry((filters, data) => filter(pipe( prop('original'), where(createFilters(filters)), ))(data)); const cars = [{"original":{"make":"audi","model":"a4"}},{"original":{"make":"bmw","model":"m5"}},{"original":{"make":"mercedes","model":"s"}},{"original":{"make":"audi","model":"a6"}}]; const filterObject = {"make":{"filters":[{"prop":"make","value":"audi"},{"prop":"make","value":"bmw"}]},"model":{"filters":[{"prop":"model","value":"a6"}]}}; const result = fn(filterObject)(cars); console.log(result);

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