javascript - 从元素创建 map 对象 JavaScript 添加或删除值

Question

我有对象

let obj1 = { categoryId:1, category:"Fruits", name:"Orange"}
let obj2 = { categoryId:1, category:"Fruits",name:"Apple"}
let obj3 = { categoryId:2, category:"Vegetables", name:"Onion"} 
let obj4 = { categoryId:2, category:"Vegetables", name:"Ginger"}....etc

我想根据这个数组创建一个 map :

{
  "Fruits": [{
    "categoryId": 1,
    "category": "Fruits",
    "name": "Orange"
  }, {
    "categoryId": 1,
    "category": "Fruits",
    "name": "Apple"
  }],
  "Vegetables": [{
    "categoryId": 2,
    "category": "Vegetables",
    "name": "Onion"
  }, {
    "categoryId": 2,
    "category": "Vegetables",
    "name": "Ginger"
  }]
}

我正在寻找一个功能来逐一添加到 map

addtoMap( obj1);
addtoMap( obj2); 
addtoMap( obj3); 
addtoMap( obj4);....etc 

同时从 map 中删除

removeFromMap( obj1);

我已经尝试过

addtoMap(xs, key) {
  return xs.reduce(function(rv, x) {
    (rv[x[key]] = rv[x[key]] || []).push(x);
    return rv;
  }, {});
};

Answer 1

您可以检查该对象是否存在并将该对象添加到所需的类别中。删除对象也是如此，直到组中不再有对象为止。然后该组也会被删除。

function addToCollection(collection, object) {
    if (!collection[object.category]) {
        collection[object.category] = [object];
        return;
    }
    if (collection[object.category].includes(object)) return;
    collection[object.category].push(object);
}

function removeFromCollection(collection, object) {
    if (!collection[object.category]) return;
    var index = collection[object.category].indexOf(object);
    if (index === -1) return;
    collection[object.category].splice(index, 1);
    if (!collection[object.category].length) delete collection[object.category];
}

var obj1 = { categoryId: 1, category: "Fruits", name:"Orange" },
    obj2 = { categoryId: 1, category: "Fruits", name:"Apple" },
    obj3 = { categoryId: 2, category: "Vegetables", name:"Onion" },
    obj4 = { categoryId: 2, category: "Vegetables", name:"Ginger" },
    collection = {};


addToCollection(collection, obj1);
addToCollection(collection, obj2);
addToCollection(collection, obj3);
addToCollection(collection, obj4);
console.log(collection);
removeFromCollection(collection, obj2);
console.log(collection);
removeFromCollection(collection, obj1);
console.log(collection);