Question

有什么方法可以使用reduce函数返回多个对象吗？例如，我想回到最年长的年龄，我有3个年龄相同的人。见下文，谢谢！

var dataArray = [
     {name: "Roy", age: 24, sex: "M"},
     {name: "Ben", age: 25, sex: "M"},
     {name: "Jamie", age: 23, sex: "F"},
     {name: "David", age: 25, sex: "M"},
     {name: "Bob", age: 25, sex: "M"}
 ];

 var oldestPeople = dataArray.reduce(function(max, cur) {
     console.log("Max is " + max["name"]);
     console.log("Cur is " + cur["name"]);
     if (cur["age"] === max["age"]) {
         return [max, cur];
     } else if (cur["age"] > max["age"]) {
         return cur;
     } else {
         return max;
     }
 });

我能够让它返回两个对象，但是一旦返回[max，cur]，我的max将变为undefined。再次感谢！

Answer 1

查看文档https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/Reduce

然后第一次回调它是前一次调用回调的返回值。

所以你遇到的问题是，有时你返回并且数组[max，cut]和其他时候你返回一个值cur或max - 只是坚持总是返回一个数组，你应该没问题，比如

 if (max)
    console.log("Max is " + max[0]["name"]);
 else
    return [cur];
 console.log("Cur is " + cur["name"]);
 if (cur["age"] === max[0]["age"]) {
     return max.concat([cur]);
 } else if (cur["age"] > max[0]["age"]) {
     return [cur].concat(max);
 } else {
     return max.concat([cur]);
 }

Answer 2

如果您想使用reduce，可以使用类似

的内容

var oldestPeople = dataArray.reduce(function(max, cur) {
  if (cur.age === max.age) {
    max.people.push(cur);
  } else if (cur.age > max.age) {
    max.age = cur.age;
    max.people = [cur];
  }
  return max;
}, {age: -Infinity, people: []}).people;

但也许我更喜欢forEach：

var maxAge = -Infinity,
    oldestPeople = [];
dataArray.forEach(function(cur) {
  if (cur.age === maxAge) {
    oldestPeople.push(cur);
  } else if (cur.age > maxAge) {
    maxAge = cur.age;
    oldestPeople = [cur];
  }
});

减少多个值

2 个答案: