轉換對象陣列散列映射，由對象的屬性值索引的

Question

使用案例

用例是對象的數組基於字符串或提供給評價函數和使用轉換成一個散列映射作爲散列表和值作爲對象本身的關鍵。使用它的常見情況是將對象數組轉換爲對象的哈希映射。

代碼

以下是在javascript一小段轉換對象數組散列地圖，由對象的屬性值索引。您可以提供一個函數來動態評估哈希映射的關鍵（運行時間）。希望這有助於未來的任何人。

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; 
}; 

您可以在這裏找到要點：https://gist.github.com/naveen-ithappu/c7cd5026f6002131c1fa

Answer 1

以下是小片段我已經在JavaScript創建轉換對象的數組哈希表，按對象的屬性值索引。您可以提供一個函數來動態評估哈希映射的關鍵（運行時間）。

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; 
}; 

您可以在這裏找到要點：https://gist.github.com/naveen-ithappu/c7cd5026f6002131c1fa

Answer 2

這是很容易做到與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舊瀏覽器，你將需要填充它。

Answer 3

使用ES6 Map（pretty well supported），你可以試試這個：

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

隨着lodash，這是可以做到使用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

使用簡單的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

採用擴頻操作：在jsFiddle代碼段

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

示範。