JS 笛卡尔积（sku）

// Array.reduce 实现
const skuReduce = (arrays) => {
  return arrays.reduce((total, next) => {
    let arr = []
    total.forEach(x => {
      next.forEach(y => {
        arr.push([x].flat().concat([y]))
      })
    })
    return arr
  })
}
skuReduce([[1,2,3],[4,5,6],[7,8,9]])

// 递归实现
export const sku = (array,results = [],num = 0) => {
  if(!results.length){
    array[num].forEach(item => {
      results.push([item])
    })
  }else{
    let resultsTwo = []
    results.forEach(result => {
      array[num].forEach(item => {
        resultsTwo.push(result.concat(item))
      })
    })
    results = resultsTwo
  }
  if(num < array.length-1){
    num++
    return sku(array,results,num)
  }else {
    return results
  }
}
sku([[1,2,3],[4,5,6],[7,8,9]])