用例

这个用例是根据提供的字符串或函数将对象数组转换为哈希映射,并将其作为哈希映射中的键来计算和使用,并将值作为对象本身。使用这种方法的常见情况是将对象数组转换为对象的哈希映射。

Code

下面是一个JavaScript小片段,用于将对象数组转换为哈希映射,以object的属性值为索引。您可以提供一个函数来动态计算散列映射的键(运行时)。

function isFunction(func) {
    return Object.prototype.toString.call(func) === '[object Function]';
}

/**
 * This function converts an array to hash map
 * @param {String | function} key describes the key to be evaluated in each object to use as key for hashmap
 * @returns Object
 * @Example 
 *      [{id:123, name:'naveen'}, {id:345, name:"kumar"}].toHashMap("id")
 *      Returns :- Object {123: Object, 345: Object}
 *
 *      [{id:123, name:'naveen'}, {id:345, name:"kumar"}].toHashMap(function(obj){return obj.id+1})
 *      Returns :- Object {124: Object, 346: Object}
 */
Array.prototype.toHashMap = function(key) {
    var _hashMap = {}, getKey = isFunction(key)?key: function(_obj){return _obj[key];};
    this.forEach(function (obj){
        _hashMap[getKey(obj)] = obj;
    });
    return _hashMap;
};

你可以在这里找到要点:将数组对象转换为HashMap。


当前回答

使用简单的Javascript

var createMapFromList = function(objectList, property) {
    var objMap = {};
    objectList.forEach(function(obj) {
      objMap[obj[property]] = obj;
    });
    return objMap;
  };
// objectList - the array  ;  property - property as the key

其他回答

使用简单的Javascript

var createMapFromList = function(objectList, property) {
    var objMap = {};
    objectList.forEach(function(obj) {
      objMap[obj[property]] = obj;
    });
    return objMap;
  };
// objectList - the array  ;  property - property as the key

我会在TypeScript中说得更清楚,以防有人感兴趣。

interface Person {
  id: number;
  name: string;
}
type Result = Map<number, string>

const input: Array<Person> = [
  {
    id: 123,
    name: "naveen"
  },
  {
    id: 345,
    name: "kumar"
  },
];
const convertedToMap: Result = input.reduce(
  (map: Result, person: Person) => {
    map.set(person.id, person.name);
    return map;
  },
  new Map()
);

简化版似乎不起作用。我跟随。

   let map = {};
    items.forEach(v=>{
      map [v.xxx] = v;
    });

使用ES6 Map(非常支持),你可以尝试这样做:

Var arr = [ {key: 'foo', val: 'bar'}, {key: 'hello', val: 'world'} ]; var result = new Map(arr。Map (i => [i。键,i.val])); //当使用TypeScript时,需要指定type: // var result = arr.map((i): [string, string] => [i]。键,i.val]) //不幸的是,映射字符串化不好。这是数组形式的内容。 console.log("Result is: " + JSON.stringify([…Result])); // Map {"foo" => "bar", "hello" => "world"}

try

let toHashMap = (a,f) => a.reduce((a,c)=> (a[f(c)]=c,a),{});

让arr = ( {id: 123,名字:“弄”}, {id: 345,名字:“kumar”} ]; 让fkey = o => o.id;//函数将对象更改为字符串(key) 让toHashMap = (f) = > a.reduce ((a、c) = > ((f (c)) = c, a), {}); console.log(toHashMap(arr,fkey)); //不推荐添加到原型: // // Array.prototype.toHashMap = function(f){返回toHashMap(this,f)}; // console.log(arr.toHashMap(fkey));