如果JS返回函数中不为空或null

function checkNumber(num) {
  if (num % 2 === 0) {
    return "偶数";
  } else {
    return "奇数";
  }
}

console.log(checkNumber(5)); // 输出：奇数

function calculateSum(arr) {
  let sum = 0;
  for (let i = 0; i < arr.length; i++) {
    sum += arr[i];
  }
  return sum;
}

let numbers = [1, 2, 3, 4, 5];
console.log(calculateSum(numbers)); // 输出：15

function createPerson(name, age) {
  return {
    name: name,
    age: age,
    introduce: function() {
      console.log("我叫" + this.name + "，今年" + this.age + "岁。");
    }
  };
}

let person = createPerson("张三", 25);
person.introduce(); // 输出：我叫张三，今年25岁。