如何在字典串列中找到值的頻率？

假設我們有以下字典陣列：

var dictionary_demo = [
                         [
                            {country: "georgia", value: sunny},
                            {country: "france", value: rainy}
                         ],
                         [
                            {country: "georgia", value: sunny},
                            {country: "france", value: gloomy}
                         ],
                         [
                            {country: "georgia", value: rainy},
                            {country: "france", value: dry}
                         ]
                      ]

我將如何獲得告訴我的輸出：

在格魯吉亞：晴天出現 2 次，雨天出現 1 次。

法國：下雨1次，陰天1次，干旱1次

uj5u.com熱心網友回復：

使用陣列陣列（JS 中字典的正確術語是陣列），很容易使用 將flatMap內部陣列中的所有值提取到外部陣列中。從那里您可以遍歷展平的陣列并收集您想要的值。

對于此示例，我可能使用該array.reduce方法將生成的平面陣列轉換為具有每個國家/地區的鍵的物件，值是具有每種天氣型別的鍵的另一個物件，以及發生頻率的值。

var dictionary_demo = [
                         [
                            {country: "georgia", value: "sunny"},
                            {country: "france", value: "rainy"}
                         ],
                         [
                            {country: "georgia", value: "sunny"},
                            {country: "france", value: "gloomy"}
                         ],
                         [
                            {country: "georgia", value: "rainy"},
                            {country: "france", value: "dry"}
                         ]
                      ]

function weatherFrequency(arr) {
  // flatten the array
  const flatArr = arr.flatMap(a => a)

  // use flattened array to transform the values into frequencies
  const sortedArr = flatArr.reduce((accum, { country, value }) => {

    // check if key exists, if not, add it
    if (!accum[country]) accum[country] = {}

    // check if weather type exists, if so add 1, if not, assign 1
    accum[country][value] ? accum[country][value]  = 1 : accum[country][value] = 1

    // return the accumulator for the next iteraction of `reduce`
    return accum
  }, {})
  return sortedArr
}

// check resulting object from the `reduce` function
console.log(weatherFrequency(dictionary_demo))

// produce a string with the values you want
const countryWeather = weatherFrequency(dictionary_demo)

// use string interpolation to extract values you need
console.log(`in georgia: sunny occurs ${countryWeather.georgia.sunny} times, and rainy occurs ${countryWeather.georgia.rainy} time`)

uj5u.com熱心網友回復：

var dictionary_demo = [
   [
      {country: "georgia", value: "sunny"},
      {country: "france", value: "rainy"}
   ],
   [
      {country: "georgia", value: "sunny"},
      {country: "france", value: "gloomy"}
   ],
   [
      {country: "georgia", value: "rainy"},
      {country: "france", value: "dry"}
   ]
]

var res = dictionary_demo.reduce(function(acc,e){
    
    return acc.concat(e);

},[]).reduce(function(acc, e){

    if(!acc[e.country])
        acc[e.country] = {[e.value]: 1};
    else
        acc[e.country][e.value] = (acc[e.country][e.value] ||  0)   1;

    return acc;
    
}, {});

console.log(res)

uj5u.com熱心網友回復：

由于這是一個陣列陣列，您可以使用 平展該陣列depth = 2，然后您可以使用該函式Array.prototype.reduce來構建所需的輸出。

const arr = [   [      {country: "georgia", value: "sunny"},      {country: "france", value: "rainy"}   ],   [      {country: "georgia", value: "sunny"},      {country: "france", value: "gloomy"}   ],   [      {country: "georgia", value: "rainy"},      {country: "france", value: "dry"}   ]];
const result = arr.flat(2).reduce((a, {country, value}) => {
  const current = (a[country] ?? (a[country] = {[value]: 0}));
  a[country][value] = (a[country][value] ?? 0)   1;
  return a;
}, {});

console.log(result);

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標籤：javascript 数组 排序 字典 频率

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