如何生成一个数组的所有子集组合，保证每个元素至少在一个子集中出现？

const arr = ['a', 'b', 'c'];

// 获取所有子集
const generatesubsets = (arr, subset = [[]]) => {
  if (arr.length === 0) {
    return subset;
  } else {
    const current = arr[0];
    const newsubset = [];
    subset.foreach(sub => {
      newsubset.push(sub.concat(current), sub);
    });
    return generatesubsets(arr.slice(1), newsubset);
  }
};

// 生成子集的差集
const generatediffsets = (arr, b) => {
  let result = [];
  for (let i = 0; i < b.length / 2; i++) {
    const diffs = arr.filter(v => b[i].indexof(v) == -1);
    result.push([b[i], diffs]);
  }

  // 添加单项子集
  const single = arr.map(i => [i]);
  result.push(single);

  return result;
};

const subsets = generatesubsets(arr);
const results = generatediffsets(arr, subsets);

console.log(results);

[[['A'], ['B', 'C']], [['B'], ['A', 'C']], [['C'], ['A', 'B']], [['A', 'B'], ['C']], [['A', 'C'], ['B']], [['B', 'C'], ['A']], [['A', 'B', 'C']]]