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如何将一个数组转换为另一个数组

arrays javascript

Sergino · 技术社区 · 7 年前

我在阵列中导航:

const arr = [
  { name: "aa", type: "total", count: 28394 },
  { name: "aa", type: "featured", count: 4 },
  { name: "aa", type: "noAnswers", count: 5816 },
  { name: "ba", type: "total", count: 148902 },
  { name: "ba", type: "featured", count: 13 },
  { name: "ba", type: "noAnswers", count: 32527 },
  { name: "cc", type: "total", count: 120531 },
  { name: "cc", type: "featured", count: 6 },
  { name: "cc", type: "noAnswers", count: 24170 }
];


const arrResult = [
  { name: "aa", total: 28394, featured: 4, noAnswers: 5816 },
  { name: "ba", total: 148902, featured: 13, noAnswers: 32527 },
  { name: "cc", total: 120531, featured: 6, noAnswers: 24170 }
];

我想出了这个密码:

let output = [];

const unique = [...new Set(arr.map(item => item.name))];

for(const key of unique) {
  let result = arr.filter(x => {
    return x.name === key;
  });
  output.push({
    name: key,
    // need to get the rest of the properties here
    // total
    // featured
    // noAnswers
  });
}

我唯一搞不懂的是如何获得房产名称。有什么想法吗?

6 回复 | 直到 7 年前

Community Mohan Dere 6 年前

你可以试试这样:

想法:

创建一个hashMap,以便通过 name .
然后,向该组添加必要的属性。
最后,在关键点上循环并创建最后一个添加了name属性的对象。

const arr = [ { name: "aa", type: "total", count: 28394 }, { name: "aa", type: "featured", count: 4 }, { name: "aa", type: "noAnswers", count: 5816 }, { name: "ba", type: "total", count: 148902 }, { name: "ba", type: "featured", count: 13 }, { name: "ba", type: "noAnswers", count: 32527 }, { name: "cc", type: "total", count: 120531 }, { name: "cc", type: "featured", count: 6 }, { name: "cc", type: "noAnswers", count: 24170 } ];

const hashMap = arr.reduce((acc, item) => {
  acc[item.name] = acc[item.name] || {};
  acc[item.name][item.type] = item.count;
  return acc;
}, {});

const result = Object.keys(hashMap).map((name) => Object.assign({}, {name}, hashMap[name] ));

console.log(result)

工作:

我所做的是为每一个新的对象创建一个新的对象 名称 .所以,这个: acc[item.name] = acc[item.name] || {}; 检查条目是否不可用。

如果不可用,请返回一个新对象。
如果可用,返回同一对象的引用。

因此,对于任何给定的名称,您将只引用同一个对象。

现在: acc[item.name][item.type] = item.count 设置属性。因为我们指的是同一个对象,所以在一个地方设置属性。所以如果你有重复的条目,比如

[
    { name: "aa", type: "total", count: 28394 },
    { name: "aa", type: "total", count: 123},
]

产量将有所增加 total: 123 相反

最后,你有一个类似的结构:

{
  aa: {
    total: <something>,
    feature: <something>,
    ...
  }
}

现在,您所要做的就是在这个对象中合并名称并返回值。还可以使用创建对象 名称 属性作为默认值( 正如 adiga ).这是我在回答问题时没有想到的。因此,赞扬而不是回答。

adiga 7 年前

你可以用 reduce 和 destructuring 这样地:

这个想法是创建一个具有 key 作为 name 属性和值作为输出中所需的最终对象。所以,你可以简单地使用 Object.values 要获取最终数组,请执行以下操作:

const arr=[{name:"aa",type:"total",count:28394},{name:"aa",type:"featured",count:4},{name:"aa",type:"noAnswers",count:5816},{name:"ba",type:"total",count:148902},{name:"ba",type:"featured",count:13},{name:"ba",type:"noAnswers",count:32527},{name:"cc",type:"total",count:120531},{name:"cc",type:"featured",count:6},{name:"cc",type:"noAnswers",count:24170}];

const merged = arr.reduce((acc,{name,type,count}) =>
  ((acc[name] = acc[name] || {name})[type] = count, acc)
,{})

console.log(Object.values(merged))

这相当于:

const arr=[{name:"aa",type:"total",count:28394},{name:"aa",type:"featured",count:4},{name:"aa",type:"noAnswers",count:5816},{name:"ba",type:"total",count:148902},{name:"ba",type:"featured",count:13},{name:"ba",type:"noAnswers",count:32527},{name:"cc",type:"total",count:120531},{name:"cc",type:"featured",count:6},{name:"cc",type:"noAnswers",count:24170}];

/* Our goal is to create a merged object like this:
{
  "aa": {
    "name": "aa",
    "total": 28394,
    "featured": 4,
    "noAnswers": 5816
  },
  "ba": {
    "name": "ba",
    "total": 148902,
    ....
  },
  "cc": {
    "name": "cc",
     ......
  }
}

The advantage of using object accumulator is we can access it like this: acc[name]
*/

const merged = arr.reduce((acc, {name,type,count} /*Destructuring*/) => {
  /* if the accumulator doesn't have the current "name" key, 
   create new object
   else use the existing one;
   {name} is same as {name: name}
  */
  acc[name] = acc[name] || {name};
  
  /* To the inner object, 
      add a key with the "type" value and assign it to "count" value
  */
  acc[name][type] = count;
  
  // return the accumulator
  return acc;
}, {})

// use Object.values to get the value part of the merged obejct into an array
console.log(Object.values(merged))

pr0p 7 年前

var op = {name : key};

  for(i=0; i < result.length; i++){
    op[result[i].type] = result[i].count;
  }

  output.push(op);

只要加上这个就行了。然而,你的代码并不是最有效的。基于名称的哈希将使其更快

const arr = [
  { name: "aa", type: "total", count: 28394 },
  { name: "aa", type: "featured", count: 4 },
  { name: "aa", type: "noAnswers", count: 5816 },
  { name: "ba", type: "total", count: 148902 },
  { name: "ba", type: "featured", count: 13 },
  { name: "ba", type: "noAnswers", count: 32527 },
  { name: "cc", type: "total", count: 120531 },
  { name: "cc", type: "featured", count: 6 },
  { name: "cc", type: "noAnswers", count: 24170 }
];

let output = [];

const unique = [...new Set(arr.map(item => item.name))];

for(const key of unique) {
  let result = arr.filter(x => {
    return x.name === key;
  });
  
  var op = {name : key};
  
  for(i=0; i < result.length; i++){
    op[result[i].type] = result[i].count;
  }
  
  output.push(op);
}

console.log(output);

以下是最有效的方法:

const arr = [
      { name: "aa", type: "total", count: 28394 },
      { name: "aa", type: "featured", count: 4 },
      { name: "aa", type: "noAnswers", count: 5816 },
      { name: "ba", type: "total", count: 148902 },
      { name: "ba", type: "featured", count: 13 },
      { name: "ba", type: "noAnswers", count: 32527 },
      { name: "cc", type: "total", count: 120531 },
      { name: "cc", type: "featured", count: 6 },
      { name: "cc", type: "noAnswers", count: 24170 }
    ];
 
 var hash = {};
 var result = [];
 
 for(var i=0; i < arr.length; i++){
  if(!arr[i].name in hash)
    hash[arr[i].name] = {}
  let temp = {};
  temp[arr[i].type] = arr[i].count;
  hash[arr[i].name] = Object.assign(temp, hash[arr[i].name]);  
 }
 
 for(var key in hash)
  result.push({name : key, ...hash[key]})
  
console.log(result)

Ashique 7 年前

你可以用 find javascript操作符从中获取所需的行 arrResult 如下图所示更改代码-

for(const key of unique) {
  let result = arr.filter(x => {
    return x.name === key;
  });
  var currResult = arrResult.find(x => x.name == key);
  output.push({
    name: key,
    // need to get the rest of the properties here
    total: currResult.total,
    featured: currResult.featured,
    noAnswers: currResult.noAnswers
  });
}

JSFiddle: https://jsfiddle.net/ashhaq12345/z8royg5w/

Nikita Malyschkin 7 年前

const arr = [
  { name: "aa", type: "total", count: 28394 },
  { name: "aa", type: "featured", count: 4 },
  { name: "aa", type: "noAnswers", count: 5816 },
  { name: "ba", type: "total", count: 148902 },
  { name: "ba", type: "featured", count: 13 },
  { name: "ba", type: "noAnswers", count: 32527 },
  { name: "cc", type: "total", count: 120531 },
  { name: "cc", type: "featured", count: 6 },
  { name: "cc", type: "noAnswers", count: 24170 }
];

const names = [...new Set(arr.map(item => item.name))]
const output = {};

names.forEach(name => {output[name] = {}});

arr.forEach(item => {
  output[item.name][item.type] = item.count
});

const result = Object.entries(output).map(([name, rest]) => ({name, ...rest}))
console.log(result);

const arrResult = [
  { name: "aa", total: 28394, featured: 4, noAnswers: 5816 },
  { name: "ba", total: 148902, featured: 13, noAnswers: 32527 },
  { name: "cc", total: 120531, featured: 6, noAnswers: 24170 }
];

Sudhir Ojha 7 年前

你可以简单地使用for循环在你的数组上进行迭代,得到一个临时数组,得到map,然后使用所需的数据填充map,然后像下面这样将map推到临时数组中。

const arr = [
  { name: "aa", type: "total", count: 28394 },
  { name: "aa", type: "featured", count: 4 },
  { name: "aa", type: "noAnswers", count: 5816 },
  { name: "ba", type: "total", count: 148902 },
  { name: "ba", type: "featured", count: 13 },
  { name: "ba", type: "noAnswers", count: 32527 },
  { name: "cc", type: "total", count: 120531 },
  { name: "cc", type: "featured", count: 6 },
  { name: "cc", type: "noAnswers", count: 24170 }
];

let result = [];
for( var i = 0; i < arr.length; i++)
{
   let data = {};
   if( arr[i].type == 'total')
   {
      data.name = arr[i].name;
      data.total = arr[i].count;
      data.featured = arr[i+1].count;
      data.noAnswers = arr[i+2].count;
      result.push(data);
   }
}

console.log(result);