javascript - if条件不满足时数组中返回空值和逗号，JS映射箭头函数

Question

我编写了以下解决方案来仅获取数组中正整数的平方

const realNumberArray = [4, 5.6, -9.8, 3.14, 42, 6, 8.34, -2];
const squareList = (arr) => {
  "use strict";
  const squaredIntegers = arr.map((val) => {

    if (val % 2 == 0 && val > 0) {
      return Math.pow(val, 2);
    }

  })

  return squaredIntegers;
};
// test your code
const squaredIntegers = squareList(realNumberArray);
console.log(squaredIntegers);

我得到的输出是 16,,,,1764,36,,

我期待的只是 16,1763,36，我试图理解当条件不满足时逗号是如何显示的。

任何有关上述问题的帮助都将不胜感激

Answer 1

在 map 之前使用过滤器

const realNumberArray = [4, 5.6, -9.8, 3.14, 42, 6, 8.34, -2];
const squareList = (arr) => {
  "use strict";
  return arr.filter(value => value>0 && value%2==0).map(value => Math.pow(value, 2));
};
// test your code
const squaredIntegers = squareList(realNumberArray);
console.log(squaredIntegers);