如何在 JavaScript 循环中合并两个 arrays

Question

Is there a better way to do this? Faster or more readable? Please share your approach.

  const a = [ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 ]
  const b = [ 'a', 'b', 'c', 'd', 'e', 'f' ]

  let i = 0
  let j = 1
  while (true) {
    const item = b[i]
    if (!item) break
    a.splice(j, 0, item)
    j += 2
    i++
  }

// expected output [0, 'a', 1, 'b', 2, 'c', 3, 'd', 4, 'e', 5, 'f', 6, 7, 8, 9]

Answer 1

My approach:

function mergeBetween(a, b) {
  let i = 0
  let j = 1
  while (true) {
    const item = b[i]
    if (!item) break
    a.splice(j, 0, item)
    j += 2
    i++
  }
  return a
}

 const a = [ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 ]
 const b = [ 'a', 'b', 'c', 'd', 'e', 'f' ]
 mergeBetween(a, b) //[0, 'a', 1, 'b', 2, 'c', 3, 'd', 4, 'e', 5, 'f', 6, 7, 8, 9]

Answer 2

You could iterate the array by the minimum of both array lengths and take the rest by slicing the arrays from the minimum length.

 function merge(a, b) { const result = []; l = Math.min(a.length, b.length); for (let i = 0; i < l; i++) result.push(a[i], b[i]); result.push(...a.slice(l), ...b.slice(l)); return result; } console.log(...merge([0, 1, 2, 3, 4, 5, 6, 7, 8, 9], ['a', 'b', 'c', 'd', 'e', 'f']));

Answer 3

You can use either recursion:

const Nil =
  Symbol();

const intercalate =
  ([x=Nil, ...xn], [y=Nil, ...yn], ret=[]) =>
    x === Nil && y === Nil
      ? ret
      : intercalate(xn, yn, ret.concat( x === Nil ? [] : x
                                      , y === Nil ? [] : y
                                      ));

Or Array#flatMap :

const intercalate =
  (xn, yn) =>
    xn.flatMap((x, i) =>
      i >= yn.length
        ? [x]
        : [x, yn[i]]);

Answer 4

This would be my approach, if speed is your game, then you should stick to for loops... But I would suggest avoiding premature optimization in general... Not sure if that is what you meant by "faster" either...

 const a = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]; const b = ["a", "b", "c", "d", "e", "f"]; // check which is longer const longer = a.length > b.length? a: b; const shorter = a.length < b.length? a: b; // declare a new variable to hold the combined array let newArray = []; for (let i = 0; i < longer.length; i++) newArray = i < shorter.length? [...newArray, longer[i], shorter[i]]: [...newArray, longer[i]]; console.log(newArray)