Question

如何从特定阵列中获取新阵列？

我不知道如何处理这样的数组：

let arr1 = [
  {name: 'a', age: 1},
  {name: 'a', age: 2},
  {name: 'a', age: 3},
  {name: 'b', age: 1},
  {name: 'b', age: 2}
  {name: 'b', age: 3}
  {name: 'c', age: 1}
  {name: 'c', age: 2}
  ...
]

“我想要这个结果：从具有相同name的每个项目中，选择最大的age值”

let arr2 = [
  {name: 'a', age: 3},
  {name: 'b', age: 3},
  {name: 'c', age: 2} 
  ...
]

Answer 1

只需使用filter为其age选择具有最高name的所有项目。

let arr1 = [{name:'a',age:1},{name:'a',age:2},{name:'a',age:3},{name:'b',age:1},{name:'b',age:2},{name:'b',age:3}];

const biggest = arr1.reduce((a, { name, age }) => {
  a[name] = a[name] || age;
  age > a[name] ? a[name] = age : a[name];
  return a;
}, {});

let arr2 = arr1.filter(({ name, age }) => biggest[name] == age);

console.log(arr2);

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Answer 2

您可以结合使用reduce和Object.values

 const arr1 = [
  {name: 'a', age: 1},
  {name: 'a', age: 2},
  {name: 'a', age: 3},
  {name: 'b', age: 1},
  {name: 'b', age: 2},
  {name: 'b', age: 3},
  {name: 'c', age: 1},
  {name: 'c', age: 2},
]

const maxNames = arr1.reduce((maxNamesObject, item) => {
  const { name, age } = item
  const maxItem = maxNamesObject[name]
  if (!maxItem || age > maxItem.age) {
    maxNamesObject[name] = item
  }
  return maxNamesObject
}, {})

const output = Object.values(maxNames)

console.log(output)

Answer 3

从此答案中提取：How to filter object array based on attributes?

您可以使用Array.prototype.filter方法：

let arr2 = arr1.filter(function (obj) {
  return obj.age === 3;
});

Answer 4

这是一个更漂亮的解决方案：

let arr1 = [
  {name: 'a', age: 1},
  {name: 'a', age: 2},
  {name: 'a', age: 3},
  {name: 'b', age: 1},
  {name: 'b', age: 2},
  {name: 'b', age: 3},
  {name: 'c', age: 1},
  {name: 'c', age: 2},
]

arr2 = Array.from(new Set(arr1.map(e => e.name))).map(e => { 
    return {
        name: e,
        age: Math.max(...arr1.filter(ee => ee.name == e).map(ee => ee.age))
    }
})

console.log(arr2)

Blockquote

Answer 5

我的解决方案：

const arr1 = [
  {name: 'a', age: 1},
  {name: 'a', age: 2},
  {name: 'a', age: 3},
  {name: 'b', age: 1},
  {name: 'b', age: 2},
  {name: 'b', age: 3},
  {name: 'c', age: 1},
  {name: 'c', age: 2},
]

let arr2 = arr1.reduce((acc, item) => {      
  let objectExists = acc.find(e => e.name === item.name)
  if (!objectExists) acc.push(item)
  else if (objectExists.age < item.age) {
      acc[acc.indexOf(objectExists)].age = item.age
  }
  return acc
}, [])

console.log(arr2)

Answer 6

我没有注意到您更新了问题。这不是最专业的代码。

  let arr1 = [
  {name: 'a', age: 1}, {name: 'a', age: 2}, {name: 'a', age: 3},
  {name: 'b', age: 1}, {name: 'b', age: 2}, {name: 'b', age: 3},
  {name: 'c', age: 1}, {name: 'c', age: 2} ];

  let names = [];
  let output = [];

  for(obj of arr1){
   if (!names.includes(obj.name)) names.push(obj.name);
  }

  for(obj of names){
    let current = arr1.filter(x => x.name === obj)
                      .reduce((a,b) => a.age > b.age ? a : b);

    output.push(current);
  }

    console.log(output);

如何从特定数组中获取新数组

6 个答案: