javascript - 从此对象中选择特定属性值时遇到问题

Question

我目前正在努力做一些相当简单的事情。我只想打印出该数组中每个对象的特定键值。如果有任何指点，我将不胜感激!

var countries = [

  {
    'country name': 'Australia',
    'national emblem': 'blue red white',
    'hemisphere': 'southern',
    'population': 24130000
  },
  {
    'country name': 'United States',
    'national emblem': 'blue red white',
    'hemisphere': 'northern',
    'population': 323000000
  },
  {
    'country name': 'Uzbekistan',
    'national emblem': 'blue green red white',
    'hemisphere': 'northern',
    'population': 31850000
  }

];


function getCountryprops(countries){
  
  for(var oneCountry in countries){
    for(var propName in oneCountry){
      console.log(oneCountry[propName]['country name'], oneCountry[propName]['population']);
    }
  }
}

所以我想最终打印出 [['澳大利亚', 24130000],['美国', 323000000],['乌兹别克斯坦', 31850000]]

Answer 1

当您使用for...in时在 countries 数组中，oneCountry 变量是当前国家/地区的索引。要获取国家/地区，您需要在 countries 数组上使用方括号表示法:

var countries = [{"country name":"Australia","national emblem":"blue red white","hemisphere":"southern","population":24130000},{"country name":"United States","national emblem":"blue red white","hemisphere":"northern","population":323000000},{"country name":"Uzbekistan","national emblem":"blue green red white","hemisphere":"northern","population":31850000}];

function getCountryprops(countries){
  for(var oneCountry in countries){
    console.log(countries[oneCountry]['country name'], countries[oneCountry]['population']);
  }
}

getCountryprops(countries);

另一个选择是使用 for...of直接获取国家的值(value):

var countries = [{"country name":"Australia","national emblem":"blue red white","hemisphere":"southern","population":24130000},{"country name":"United States","national emblem":"blue red white","hemisphere":"northern","population":323000000},{"country name":"Uzbekistan","national emblem":"blue green red white","hemisphere":"northern","population":31850000}];

function getCountryprops(countries){
  for(var oneCountry of countries){
    console.log(oneCountry['country name'], oneCountry['population']);
  }
}

getCountryprops(countries);