转换对象阵列散列映射，由对象的属性值索引的

Question

使用案例

用例是对象的数组基于字符串或提供给评价函数和使用转换成一个散列映射作为散列表和值作为对象本身的关键。使用它的常见情况是将对象数组转换为对象的哈希映射。

代码

以下是在javascript一小段转换对象数组散列地图，由对象的属性值索引。您可以提供一个函数来动态评估哈希映射的关键（运行时间）。希望这有助于未来的任何人。

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 hasmap 
* @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; 
}; 

您可以在这里找到要点：https://gist.github.com/naveen-ithappu/c7cd5026f6002131c1fa

Answer 1

以下是小片段我已经在JavaScript创建转换对象的数组哈希表，按对象的属性值索引。您可以提供一个函数来动态评估哈希映射的关键（运行时间）。

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 hasmap 
* @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; 
}; 

您可以在这里找到要点：https://gist.github.com/naveen-ithappu/c7cd5026f6002131c1fa

Answer 2

这是很容易做到与Array.prototype.reduce：

var arr = [ 
    { key: 'foo', val: 'bar' }, 
    { key: 'hello', val: 'world' } 
]; 

var result = arr.reduce(function(map, obj) { 
    map[obj.key] = obj.val; 
    return map; 
}, {}); 

console.log(result); 
// { foo: 'bar', hello: 'world' } 

注：Array.prototype.reduce()是IE9 +，所以如果你需要支持旧浏览器，你将需要填充它。

Answer 3

使用ES6 Map（pretty well supported），你可以试试这个：

var arr = [ 
    { key: 'foo', val: 'bar' }, 
    { key: 'hello', val: 'world' } 
]; 

var result = new Map(arr.map((i) => [i.key, i.val])); 

// When using TypeScript, need to specify type: 
// var result = arr.map((i): [string, string] => [i.key, i.val]) 

console.log(result); 
// Map {"foo" => "bar", "hello" => "world"} 

Answer 4

随着lodash，这是可以做到使用keyBy：

var arr = [ 
    { key: 'foo', val: 'bar' }, 
    { key: 'hello', val: 'world' } 
]; 

var result = _.keyBy(arr, o => o.key); 

console.log(result); 
// Object {foo: Object, hello: Object} 

Answer 5

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 

Answer 6

es2015版本：

const myMap = new Map(objArray.map(obj => [ obj.key, obj.val ])); 

Answer 7

采用扩频操作：在jsFiddle代码段

const result = arr.reduce(
    (accumulator, target) => ({ ...accumulator, [target.key]: target.val }), 
    {}); 

示范。