如何使用 ramda 库组合两个数组？

Question

I have two array as below

const l1 = [ {"a": 1, "a1": 2}, {"b": 3, "b1": 4}, {"c": 5, "c1": 6} ];
const l2 = [ {"d": 2}, {"e": 2}, {"f": 2} ];

How can I use ramda library to combine these two and get result like

[ {"a": 1, "a1": 2, "d": 2}, {"a": 1, "a1": 2, "e": 2}, {"a": 1, "a1": 2, "f": 2}, 
{"b": 3, "b1": 4, "d": 2}, {"b": 3, "b1": 4, "e": 2}, {"b": 3, "b1": 4, "f": 2}, 
{"c": 5, "c1": 6, "d": 2}, {"c": 5, "c1": 6, "e": 2}, {"c": 5, "c1": 6, "f": 2} ]

I used

R.map(R.xprod(__, l2, l1)

But not working since i got object inside array.

Thanks in advance.

Answer 1

To get a Cartesian product of two arrays of objects you can create a function by lifting merge:

 const fn = R.lift(R.merge) const l1 = [ {"a": 1, "a1": 2}, {"b": 3, "b1": 4}, {"c": 5, "c1": 6} ]; const l2 = [ {"d": 2}, {"e": 2}, {"f": 2} ]; const result = fn(l1, l2) console.log(result)

 .as-console-wrapper { max-height: 100% !important; top: 0; }

 <script src="https://cdnjs.cloudflare.com/ajax/libs/ramda/0.27.0/ramda.js" integrity="sha256-buL0byPvI/XRDFscnSc/e0q+sLA65O9y+rbF+0O/4FE=" crossorigin="anonymous"></script>

Answer 2

With plain Javascript, you could take cartesian product with a double nested reduce by mapping new objects.

This approach works for an arbirary count of arrays (sort of ...).

 const l1 = [{ a: 1, a1: 2 }, { b: 3, b1: 4 }, { c: 5, c1: 6 }], l2 = [{ d: 2 }, { e: 2 }, { f: 2 }], result = [l1, l2].reduce((a, b) => a.reduce((r, v) => r.concat(b.map(w => ({ ...v, ...w }))), [])); console.log(result);

 .as-console-wrapper { max-height: 100% !important; top: 0; }

Answer 3

If not very particular about ramda, you can do as below with one line using flatMap and map .

 const l1 = [ { a: 1, a1: 2 }, { b: 3, b1: 4 }, { c: 5, c1: 6 } ]; const l2 = [{ d: 2 }, { e: 2 }, { f: 2 }]; const merged = l2.flatMap(item2 => l1.map(item1 => ({ ...item1, ...item2 }))); console.log(JSON.stringify(merged));

Answer 4

There is another option to merge arrays using R.reduce function

const input = {
  arr1: ['a', 'b'],
  arr2: ['c', 'd']
}

R.compose(
  R.reduce((acc, cur) => {
    return [...acc, ...cur]
  }, []),
  R.map(([key, value]) => value),
  R.toPairs
)(input)