根据已有数组向数组对象添加属性和属性值

问题： 将arr1中的元素分别添加到arr2中，作为hobby的属性值，自动生成多对象的数组arr3

    const arr1 = ["aa", "bb", "cc", "dd"];
    const arr2 = [{ name: "tom", age: 18 }];

    const arr3 = [
      { name: "tom", age: 18, hobby: "aa" },
      { name: "tom", age: 18, hobby: "bb" },
      { name: "tom", age: 18, hobby: "cc" },
      { name: "tom", age: 18, hobby: "dd" },
    ];

const arr3 = arr1.map（item => return {…arr2【0】，…item}）