如何使用 ramda 库合并两个数组？

Question

我有两个数组如下

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

如何使用 ramda 库将这两者结合起来并获得类似

的结果

[ {"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} ]

我用过

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

但由于我在数组中得到了对象，所以无法正常工作。

提前致谢。

Answer 1

对于普通 Javascript，您可以通过映射新对象将 笛卡尔积 与双嵌套归约相结合。

这种方法适用于数组的任意计数（有点……）。

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);

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Answer 2

如果对ramda不是很讲究的话，你可以用flatMap和map.

一行来做

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 3

要获得两个对象数组的笛卡尔积，您可以通过提升合并创建一个函数：

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)

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<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 4

还有一个选项可以使用R.reduce函数合并数组

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)

如何使用 ramda 库合并两个数组？

How to combine two array using ramda library?

javascript

ramda.js