[英]Merge two arrays by grouping based on elements of 1st array in Javascript
我有兩個這樣的數組(arr1&arr2)
var arr1 = ["A","B","C"];
var arr2 = [["A","aa"], ["A","ab"], ["A","ac"],["B","ba"],["B","bb"],["B","bc"],["C","ca"],["C","cb"]];
我想根據第一個數組的值將它們組合到javascript中的第三個數組中。 所需輸出:
arr3 = [ ["A",["aa","ab","ac"]], ["B",["ba","bb","bc"] ], ["C",["ca","cb"]] ]
注意:我從arr2開始,並且能夠檢索第一個值並將重復項刪除到arr1中。
請指教。
這樣嘗試
var arr1 = ["A", "B", "C"];
var arr2 = [
["A", "aa"],
["A", "ab"],
["A", "ac"],
["B", "ba"],
["B", "bb"],
["B", "bc"],
["C", "ca"],
["C", "cb"]
];
var newVal = arr1.map(function(x) {
var filter = arr2.filter(function(y) {
return y[0] == x;
}).map(function(y) {
return y[1];
});
return [x, filter];
})
console.log(newVal);
注意:我從arr2開始,並且能夠檢索第一個值並將重復項刪除到arr1中。
與其創建arr1
作為中間步驟,不如創建一個對象作為中間步驟:
var obj = arr2.reduce(function(a,b){
if (!a[b[0]]) a[b[0]] = [];
a[b[0]].push(b[1]);
return a;
},{});
// obj is now {"A":["aa","ab","ac"],"B":["ba","bb","bc"],"C":["ca","cb"]}
將該對象轉換為所需的輸出數組:
var arr3 = Object.keys(obj).map(function(v) { return [v, obj[v]]; });
// [["A",["aa","ab","ac"]],["B",["ba","bb","bc"]],["C",["ca","cb"]]]
如果您實際上還需要arr1
數組用於其他操作,則:
var arr1 = Object.keys(obj);
// ["A", "B", "C"]
但是請注意, obj
對於進一步處理非常有用,因為如果您需要獲取與"B"
關聯的值,則無需再次搜索數組,您只需說出obj["B"]
(這將給出數組["ba","bb","bc"]
)。 因此,第二個"B"
值是obj["B"][1]
。
進一步閱讀:
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