Question

要求是获取对象数组中每个“用户”的前X个score。

对象数组已按用户，得分进行排序。

例如，如果它是我们之后的“前3个”，并且用户“ barney”的数组中有4行-然后从用户数组中返回前3个元素 “巴尼”。

另一个例子：如果它是我们排在后面的“前3名”，并且用户在数组中有2个元素，则返回这2个元素。

这是我想要TOP 3的示例：

var users = [
 { user: 'barney', score: 39},
 { user: 'barney', score: 37},
 { user: 'barney', score: 36},
 { user: 'barney', score: 36},
 { user: 'fred', score: 40},  
 { user: 'fred', score: 22},
 { user: 'wilma', score: 40},
 { user: 'wilma', score: 40}
];

因此在此示例中，结果应为：

[
 { user: 'barney', score: 39},
 { user: 'barney', score: 37},
 { user: 'barney', score: 36},
 { user: 'fred', score: 40},
 { user: 'fred', score: 22},
 { user: 'wilma', score: 40},
 { user: 'wilma', score: 40}
];

Answer 1

没有lodash也有可能，所以有了lodash也有可能。

按用户拆分原始数组，使用slice保留第一个x，将所有内容合并回1个数组。

var users = [
 { user: 'barney', score: 39},
 { user: 'barney', score: 37},
 { user: 'barney', score: 36},
 { user: 'barney', score: 36},
 { user: 'fred', score: 40},  
 { user: 'fred', score: 22},
 { user: 'wilma', score: 40},
 { user: 'wilma', score: 40}
];
var x = 3;

var names = users.reduce((acc, n) => {
  acc.add(n.user);
  return acc;
}, new Set());
var groups = [...names].reduce((acc, n) => {
  acc.push(users.filter(m => m.user === n));
  return acc;
}, []);
groups = groups.map(n => n.slice(0, x));
var result = groups.reduce((acc, n) => {
  acc.push(...n);
  return acc;
}, []);
console.log(result);

Answer 2

假设const getTop = (users, top, counts = {}) => users.filter(({ user }) => (counts[user] = (counts[user] || 0) + 1) <= top);集合已经按名称和分数排序，则可以简单地通过使用Array#filter来实现。

var users = [
  { user: 'barney', score: 39},
  { user: 'barney', score: 37},
  { user: 'barney', score: 36},
  { user: 'barney', score: 36},
  { user: 'fred', score: 40},  
  { user: 'fred', score: 22},
  { user: 'wilma', score: 40},
  { user: 'wilma', score: 40}
];

const getTop = (users, top, counts = {}) => 
  users.filter(({ user }) => (counts[user] = (counts[user] || 0) + 1) <= top);

console.log('TOP 1', getTop(users, 1));
console.log('TOP 2', getTop(users, 2));
console.log('TOP 3', getTop(users, 3));

.as-console-wrapper{min-height:100%;}

char

如何通过过滤器在对象数组中获得最高的X（Javascript）

2 个答案: