如何筛选仅等于数组中项的映射

Question

你好，伙计们，我有一张这样的地图Map {'708335088638754946' => 38772,'712747381346795670' => 12051,'712747409108762694' => 12792 }我有一个数组，如let array = ["712747381346795670", "708335088638754946"]如何过滤仅等于数组中项的映射

Answer 1

const oldMap = new Map([["a", "1"], ["b", "2"], ["c", "3"]]);

const array = ["a", "c"];

const newMap = new Map(array.map(key => [key, oldMap.get(key)]));

// newMap is the same as oldMap but only with keys from array

或

const oldMap = new Map([["a", "1"], ["b", "2"], ["c", "3"]]);

const array = ["a", "c"];

const newMap = new Map([...oldMap.entries()].filter(entry => array.includes(entry[0])))

// newMap is the same as oldMap but only with keys from array

Answer 2

您可以按如下方式将该函数与该函数一起使用：Object.entriesArray.prototype.map

let data = {'708335088638754946': 38772,'712747381346795670': 12051,'712747409108762694': 12792 };

let array = ["712747381346795670", "708335088638754946"];

let result = Object.entries(data)

      .filter(([k]) => array.includes(k))

      .map(([key,value]) => ({[key]: value}));

      

console.log(result);

另一种方法可能是函数Array.prototype.reduce

let data = {'708335088638754946': 38772,'712747381346795670': 12051,'712747409108762694': 12792 };

let array = ["712747381346795670", "708335088638754946"];

let result = Object.entries(data)

      .reduce((a, [k, v]) => a.concat(array.includes(k) ? {[k]: v} : []), []);

      

console.log(result);

使用对象Map

let data = new Map([['708335088638754946', 38772],['712747381346795670', 12051], ['712747409108762694', 12792]]);

let array = ["712747381346795670", "708335088638754946"];

let result = new Map(Array.from(data.keys())

      .reduce((a, k) => a.concat(array.includes(k) ? [[k, data.get(k)]] : []), []));

console.log(result.has("712747409108762694"));

console.log(result.has("708335088638754946"));

console.log(result.has("712747381346795670"));

Answer 3

const map = new Map([["a", "b"], ["c", "d"], ["e", "f"]]);

const array = ["a", "c"];

console.log(map);

for (let [prop, value] of map) {

  if (array.includes(prop)) {

    // collect matched items here

  }

}

Answer 4

您可以只循环访问所有条目，只将匹配的条目添加到结果中：

const result = new Map();

const array = ["712747381346795670", "708335088638754946"];

for( const [ key, value ] of input.entries() ) {

  if( array.includes( key ) ) {

    result.set( key, value );

  }

}