Question

{{1}}

我有一个企业的对象列表（分配了一个ID），每个企业都有自己的国家。

我的问题是通过财产查找金额的最佳方法是什么？例如，如果我想查找法国企业的总数，它将根据代码示例返回3。

Answer 1

您可以尝试这样的事情：

var Business = {
    1: {Country:"France"}
  , 2: {Country:"United Kingdom"}
  , 3: {Country:"France"}
  , 4: {Country:"France"}
};

var businessInFrance = Object.keys(Business)
                             .map(key => Business[key])
                             .reduce(function(acc, val){
                                 return val.Country === "France"
                                       ? acc+=1
                                       : acc;
                                 },0);
                        
console.log(businessInFrance);

Object.keys(Business)返回一个数组，其中包含Business拥有的可枚举
map将我们传递的函数应用于上一步的输出并返回一个新数组。此数组的元素是Business
reduce应用我们为上一步数组的每个元素传递的函数，当Country属性的值等于“France”时，我们将累加器的值递增1 ，acc，否则我们将保持不变。然后返回累加器的值。

Answer 2

您的对象存在问题。您可以使用以下内容，但我不得不问为什么不使用数组？

Business = {
  01: {Country:"France"},
  02: {Country:"United Kingdom"},
  03: {Country:"France"},
  04: {Country:"France"},
}

const BusinessArray = [
  {Country:"France"},
  {Country:"United Kingdom"},
  {Country:"France"},
  {Country:"France"},
]

console.log(
  BusinessArray.filter(x => x.Country === 'France').length
)

Business = {
  01: {Country:"France"},
  02: {Country:"United Kingdom"},
  03: {Country:"France"},
  04: {Country:"France"},
}

const countriesCount = (country, businesses) => 
  Object.keys(businesses)
    .filter(x => businesses[x].Country === country)
    .length
    
console.log(
  countriesCount('France', Business),
  countriesCount('United Kingdom', Business)
)

Answer 3

您可以使用对象来计算国家/地区。

＆＃13;

var business = { 1: { Country: "France" }, 2: { Country: "France" }, 3: { Country: "UnitedKingdom" }, 4: { Country: "France" } },
    count = Object.keys(business).reduce(function (r, k) {
        var country = business[k].Country;
        r[country] = (r[country] || 0) + 1;
        return r;
    }, Object.create(null));

console.log(count.France);
console.log(count);

＆＃13;

.as-console-wrapper { max-height: 100% !important; top: 0; }

＆＃13;

Answer 4

首先，您的语法不正确，会导致错误。

如果你包含数组中的所有对象，你就不需要这些对象来维护自己的标识符，你可以很容易地做到这一点：

＆＃13;

var business = [
   {country:"France"},
   {country:"United Kingdom"},
   {country:"France"},
   {country:"France"}
];


console.log("The amount of countries is: " +  business.length);

var count = 0;
business.forEach(function(value){
   count = (value.country === "France") ? ++count : count;
});

console.log("The amount of times France appears is: " + count);

＆＃13;

Answer 5

Object.keys返回对象的键。您可以循环键并计算您想要的结果。这是一个例子..

＆＃13;

var Business =  {
1:{
  Country: "France"
},
2:{
  Country: "France"
},
3:{
  Country: "UnitedKingdom"
},
4:{
  Country: "France"
}};

var countByCountry = function(country){
  var result = 0;
  Object.keys(Business).forEach(function(it){
    result += (Business[it].Country === country ? 1 : 0);
    console.log(it, country, result);
  });
  return result;
}

console.log(countByCountry('France'));

＆＃13;

根据属性计算对象中的项目总数

5 个答案: