Question

包括18-25岁之间的潜在选民人数，26-35岁之间的潜在选民，36-55岁之间的潜在选民以及每个年龄范围内的实际投票人数。包含此数据的结果对象应具有6个属性。

var voters = [
    {name:'Bob' , age: 30, voted: true},
    {name:'Jake' , age: 32, voted: true},
    {name:'Kate' , age: 25, voted: false},
    {name:'Sam' , age: 20, voted: false},
    {name:'Phil' , age: 21, voted: true},
    {name:'Ed' , age:55, voted:true},
    {name:'Tami' , age: 54, voted:true},
    {name: 'Mary', age: 31, voted: false},
    {name: 'Becky', age: 43, voted: false},
    {name: 'Joey', age: 41, voted: true},
    {name: 'Jeff', age: 30, voted: true},
    {name: 'Zack', age: 19, voted: false}
];

function voterResults(arr) {
   // your code here
}

console.log(voterResults(voters)); // Returned value shown below:
/*
{ youngVotes: 1,
  youth: 4,
  midVotes: 3,
  mids: 4,
  oldVotes: 3,
  olds: 4 
}

我正在尝试解决此特定问题，以下是我尝试过的能够形成哈希图的地方。但不确定如何解决上述问题。

function voterResults(arr) {
  let votesArray = ['youngVotes', 'youth', 'midVotes', 'mids', 
      'oldVotes', 'olds']
   return votesArray.reduce((acc, it) => {
     acc[it] = (acc[it] || 0) + 1  
     return acc;
   }, {})
}

//输出

{
   youngVotes: 1 ,
   youth: 1 ,
   midVotes: 1 ,
   mids: 1 ,
   oldVotes: 1 ,
   olds: 1
}

需要实际输出：

{
  youngVotes: 1,
  youth: 4,
  midVotes: 3,
  mids: 4,
  oldVotes: 3,
  olds: 4 
}

Answer 1

我首先要创建一个辅助函数，该函数返回与传递的年龄相对应的属性字符串（例如20-> ['youth', 'youngVotes']）。然后使用.reduce遍历voters数组-调用该函数以找出要递增的属性，然后递增该属性：

const getCat = (age) => {
  if (age < 25) return ['youth', 'youngVotes'];
  if (age < 35) return ['mids', 'midVotes'];
  return ['olds', 'oldVotes'];
};
var voters = [
    {name:'Bob' , age: 30, voted: true},
    {name:'Jake' , age: 32, voted: true},
    {name:'Kate' , age: 25, voted: false},
    {name:'Sam' , age: 20, voted: false},
    {name:'Phil' , age: 21, voted: true},
    {name:'Ed' , age:55, voted:true},
    {name:'Tami' , age: 54, voted:true},
    {name: 'Mary', age: 31, voted: false},
    {name: 'Becky', age: 43, voted: false},
    {name: 'Joey', age: 41, voted: true},
    {name: 'Jeff', age: 30, voted: true},
    {name: 'Zack', age: 19, voted: false}
];

const counts = voters.reduce((a, { age, voted }) => {
  const [prop, voteProp] = getCat(age);
  a[prop] = (a[prop] || 0) + 1;
  if (voted) {
    a[voteProp] = (a[voteProp] || 0) + 1;
  }
  return a;
}, {});
console.log(counts);

Answer 2

您需要使用输入arr，已投票的使用值以及年龄来对对象中的值进行分类和递增。

const voters = [
    {name:'Bob' , age: 30, voted: true},
    {name:'Jake' , age: 32, voted: true},
    {name:'Kate' , age: 25, voted: false},
    {name:'Sam' , age: 20, voted: false},
    {name:'Phil' , age: 21, voted: true},
    {name:'Ed' , age:55, voted:true},
    {name:'Tami' , age: 54, voted:true},
    {name: 'Mary', age: 31, voted: false},
    {name: 'Becky', age: 43, voted: false},
    {name: 'Joey', age: 41, voted: true},
    {name: 'Jeff', age: 30, voted: true},
    {name: 'Zack', age: 19, voted: false}
];

// define your limit here, will check for <= of defined age
let categories = { youngVotes: 21, youth: 30, midVotes: 40, mids: 50, oldVotes: 60, olds: 130}

function voterResults(arr) {
const conditions = Object.entries(categories);
   return arr.reduce((val, vote)=>{
        if(vote.voted) {

        for(let i=0;i<conditions.length;i++) {
            if(vote.age <= conditions[i][1]) {
            val[conditions[i][0]] = val[conditions[i][0]] ? val[conditions[i][0]] + 1 : 1;
            return val;
          }
        }
      }
      return val;
   }, {})
}

console.log(voterResults(voters));

Answer 3

这里使用的是reduce方法，可以轻松扩展年龄段。

function voterResults(arr) {
  const ranges = { youngVotes: [18, 25], youth: [26, 35] };

  return arr
    .filter(x => x.voted)
    .reduce((acc, curr) => {
      Object.keys(ranges).forEach(key => {
        if (curr.age >= ranges[key][0] && curr.age <= ranges[key][1]) {
          acc[key] = key in acc ? acc[key] + 1 : 1;
        }
      });
      return acc;
    }, {});
}

var voters = [
  { name: "Bob", age: 30, voted: true },
  { name: "Jake", age: 32, voted: true },
  { name: "Kate", age: 25, voted: false },
  { name: "Sam", age: 20, voted: false },
  { name: "Phil", age: 21, voted: true },
  { name: "Ed", age: 55, voted: true },
  { name: "Tami", age: 54, voted: true },
  { name: "Mary", age: 31, voted: false },
  { name: "Becky", age: 43, voted: false },
  { name: "Joey", age: 41, voted: true },
  { name: "Jeff", age: 30, voted: true },
  { name: "Zack", age: 19, voted: false }
];

console.log(voterResults(voters));

Answer 4

您可以简单地使用if条件

response.css('[itemprop="url"] ::attr(href)').extract_first()

查找对象数组中的总数

4 个答案: