使用 javascript 组合两个 arrays 的最佳方法是什么？

Question

I'm going to write a function that creates an array like this

["0-AA", "0-BB", "1-AA", "1-BB", "2-AA", "2-BB", "3-AA", "3-BB"]

This function, to be exact, is a combination of the following two arrays with a separator '-'. ex:

arr1 = [0,1,2,3]    //number
arr2 = ["AA", "BB"]  //produce code

The result is always equal to the product of the length of the two arrays The size of both arrays is subject to change The first array is always an integer

I want to know a good way to combine the arrays according to the rules. Is it possible to write with an array-only function such as map, concat, etc. without repetitive statements such as for statements?

Answer 1

This is called Carthesian product , and requires one loop per array. Here, I use map and flatMap for this purpose.

 function product(a, b, sep) { return a.flatMap(ae => b.map(be => ae + sep + be)) } const arr1 = [0,1,2,3] const arr2 = ["AA", "BB"] const result = product(arr1, arr2, "-") console.log(result)

Or, a generalised version, where product takes any number of arrays and returns the tuples, and you can join them yourself. The extra loop, provided by reduce , iterates over the input arrays.

 function product(...arrs) { return arrs.reduce( (result, arr) => result.flatMap(re => arr.map(ae => re.concat([ae])) ), [[]], ) } const arr1 = [0,1,2,3] const arr2 = ["AA", "BB"] const result = product(arr1, arr2).map(items => items.join('-')) console.log(result)

Answer 2

You can use .reduce and .forEach

arr1 = [....]
arr2 = [....]

result = arr1.reduce((acc,value) => {
  arr2.forEach(str => acc.push(`${value}-${str}`))
  return acc;
}, [])

Answer 3

While you certainly can do it the way others have shown

const array1 = [1, 2, 3]
const array2 = ['a', 'b', 'c']

const product = array1
    .reduce((product, value1) => (
        product.push(array2.map(value2 => value1 + '-' + value2)),
        product), [])
    .flat()

I'd suggest using a more traditional function with for loops as there is a slight performance gain in speed and memory usage.

function product(array1, array2, separator = '') {
    const product = []
    for (let i = 0; i < array1.length; ++i)
        for (let j = 0; j < array2.length; ++j)
            product.push(array1[i] + separator + array2[j])
    return product
}

Answer 4

For your last requirement,

Is it possible to write with an array-only function such as map, concat, etc. without repetitive statements such as for statements?

I assume you accept array.forEach() .

 const arr1 = [0,1,2,3]; const arr2 = ["AA", "BB"] const result = [] arr1.forEach((number)=>{ arr2.forEach((code)=>{ result.push(`${number}-${code}`) }) }) console.log(result)