複数の配列を同じキーで結合する

Question

複数の配列を特定のkeyプロパティで結合しようとしています。例えば、私はどのように私は、次のARR3を作るのですか？

[{ 
    key: 'B', 
    items: [{name: 'another b item'}, {name: 'more b items'}, {name: 'even more b items'}] 
    }] 

ARR2

ARR1

[{ 
    key: 'A', 
    items: [{name: 'a item'}] 
    }, { 
    key: 'B', 
    items: [{name: 'b item'}] 
    }] 

を持っていますか

[{ 
    key: 'A', 
    items: [{name: 'a item'}] 
    }, 
    { 
    key: 'B', 
    items: [{name: 'b item'}, {name: 'another b item'}, {name: 'more b items'}, {name: 'even more b items'}] 
    }] 

Answer 1

は、このようなハッシュテーブルを使用することもできます。

arr1=[{ 
 
    key: 'A', 
 
    items: [{name: 'a item'}] 
 
    }, { 
 
    key: 'B', 
 
    items: [{name: 'b item'}] 
 
    }]; 
 

 
arr2=[{ 
 
    key: 'B', 
 
    items: [{name: 'another b item'}, {name: 'more b items'}, {name: 'even more b items'}] 
 
    }]; 
 
    
 
console.log(arr1.concat(arr2).reduce((function(hash){ 
 
    return function(array,obj){ 
 
    if(!hash[obj.key]) 
 
    array.push(hash[obj.key]=obj); 
 
    else 
 
     hash[obj.key].items.push(...obj.items); 
 
    return array; 
 
    };  
 

 
})({}),[]));

いくつかの説明：

arr1.concat(arr2)//just work with one array as its easier 
.reduce(...,[]));//reduce this array to the resulting array 
//through 
(function(hash){//an IIFE to closure our hash object 
... 
})({}) 
//which evaluates to 
    function(array,obj){//take the resulting array and one object of the input 
    if(!hash[obj.key])//if we dont have the key yet 
    array.push(hash[obj.key]=obj);//init the object and add to our result 
    else 
     hash[obj.key].items.push(...obj.items);//simply concat the items 
    return array; 
    };  

Answer 2

スニペット私は同様のために何度も使用したことを持っています。ユースケースの名前が変更されました。

var output = array.reduce(function(o, cur) { 

    // Get the index of the key-value pair. 
    var occurs = o.reduce(function(k, item, i) { 
    return (item.key === cur.key) ? i : k; 
    }, -1); 

    // If the name is found, 
    if (occurs >= 0) { 

    // append the current value to its list of values. 
    o[occurs].item = o[occurs].value.concat(cur.items); 

    // Otherwise, 
    } else { 

    // add the current item to o (but make sure the value is an array). 
    var obj = {key: cur.key, item: [cur.items]}; 
    o = o.concat([obj]); 
    } 

    return o; 
}, []); 

Answer 3

var arr1 = [{ 
 
    key: 'A', 
 
    items: [{name: 'a item'}] 
 
    }, { 
 
    key: 'B', 
 
    items: [{name: 'b item'}] 
 
    }] 
 
var arr2 = [{ 
 
    key: 'B', 
 
    items: [{name: 'another b item'}, {name: 'more b items'}, {name: 'even more b items'}] 
 
    }] 
 
    
 
    
 
var arr3 = _.map(_.groupBy(arr1.concat(arr2), 'key'), 
 
    val => ({ 
 
    key : val[0].key, items: _.union.apply(this,val.map(v => v.items)) 
 
    }) 
 
) 
 
console.log(arr3)

<script src="https://cdnjs.cloudflare.com/ajax/libs/underscore.js/1.8.3/underscore-min.js"></script>