javascript使用ID列表从嵌套数组中提取对象

Question

我有一个ID列表作为参考，并且我有一个对象，其中包含具有对象数组的多个对象。

我想以最快的方式在列表中创建具有相应ID的对象数组。

 const data = { "items": { "item1": [{ "id": "id1", "info": "info1" }, { "id": "id2", "info": "info22" } ], "item20": [{ "id": "id3", "info": "info5" }], "item5": [{ "id": "id4", "info": "info6" }, { "id": "id5", "info": "info7" } ] } }; const keep = ['id4', 'id2']; const results = []; keep.forEach(function(val) { const match = Object.keys(data.items).map(item => { return data.items[item].find(obj => obj.id === val) }); results.push(match) }) console.log('final: ', results) 

当前没有返回我想要的。 预期结果将是：

[
    {
      "id": "id2",
      "info": "info22"
    },
    {
        "id": "id4",
        "info": "info6"
    }
]

更新：

如果数据本身是对象数组，又想对每个对象做同样的事情，该怎么办？

  const data = [{ "otherStuff": "otherB", "items": { "item1": [{ "id": "id1", "info": "info1" }, { "id": "id2", "info": "info22" } ], "item20": [{ "id": "id3", "info": "info5" }], "item5": [{ "id": "id4", "info": "info6" }, { "id": "id5", "info": "info7" } ] } }, { "otherStuff": "otherA", "items": { "item1": [{ "id": "id1", "info": "info10000" }, { "id": "id2", "info": "info220000" } ], "item20": [{ "id": "id3", "info": "info5000" }], "item5": [{ "id": "id4", "info": "info60000" }, { "id": "id5", "info": "info7000" } ] } }]; const keep = ['id4', 'id2']; const results = []; keep.forEach(function(val) { data.forEach(function(entry){ Object.keys(entry.items).forEach(item => { var match = entry.items[item].find(obj => obj.id === val); if (match) { results.push(match) } }); }); }) console.log(results) 

输出应为：

[
    {
        "otherStuff": "otherB",
        "items": [
                {
                      "id": "id2",
                      "info": "info22"
                },
                {
                    "id": "id4",
                    "info": "info6"
            }
        ]
    },
    {
        "otherStuff": "otherA",
        "items": [
                {
                      "id": "id2",
                      "info": "info220000"
                },
                {
                    "id": "id4",
                    "info": "info60000"
            }
        ]
    }
]

结果却不一样。

Answer 1

如果将Set用作保留的id，则保存一个O（n）遍历：

 const keep = new Set(['id4', 'id2']);

 const result = [];

 for(const items of Object.values(data.items))
   for(const item of items)
     if(keep.has(item.id))
       result.push(item);

Answer 2

您不需要使用map() 。 只需在要保留的对象键上使用forEach()循环，然后找到匹配的对象，即可将其推入结果数组。

 const data = { "items": { "item1": [{ "id": "id1", "info": "info1" }, { "id": "id2", "info": "info22" } ], "item20": [{ "id": "id3", "info": "info5" }], "item5": [{ "id": "id4", "info": "info6" }, { "id": "id5", "info": "info7" } ] } }; const keep = ['id4', 'id2']; const results = []; keep.forEach(function(val) { Object.keys(data.items).forEach(item => { var match = data.items[item].find(obj => obj.id === val); if (match) { results.push(match) } }); }) console.log('final: ', results) 

Answer 3

items是一个对象＆ item1 ， item20是键。因此，您可以执行Object.values并在其上应用reduce函数以获得包含所有对象的单个数组。 无需迭代keep数组并从单个数组中过滤出所需的元素。

 const data = { "items": { "item1": [{ "id": "id1", "info": "info1" }, { "id": "id2", "info": "info22" } ], "item20": [{ "id": "id3", "info": "info5" }], "item5": [{ "id": "id4", "info": "info6" }, { "id": "id5", "info": "info7" } ] } }; const keep = ['id4', 'id2']; let getAllObjectValues = Object.values(data.items).reduce(function(acc, curr) { curr.forEach((elem) => { acc.push(elem) }) return acc; }, []); let k = keep.map(function(item) { return getAllObjectValues.filter(function(val) { return item === val.id })[0] }) console.log(k) 

Answer 4

您在地图函数中使用了赋值运算符而不是等价运算符，请更改为：

const keep = ['id4', 'id2'];
const results = [];
keep.forEach(function(val){
    const match = Object.keys(data.items).map(item => {
        return data.items[item].find(obj => obj.id === val)
    });
    results.push(match)
})
console.log('final: ', results)    

Answer 5

结合使用reduce和filter ，可以迭代每个子数组，检查是否应保留该值。

 const data = { "items": { "item1": [ { "id": "id1", "info": "info1" }, { "id": "id2", "info": "info22" } ], "item20": [ { "id": "id3", "info": "info5" } ], "item5": [ { "id": "id4", "info": "info6" }, { "id": "id5", "info": "info7" } ] } }; const keep = ['id4', 'id2']; const filter = el => { return keep.indexOf(el.id) >= 0; }; const reducer = (accumulator, currentValue) => { return accumulator = accumulator.concat(data.items[currentValue].filter(filter)); }; let results = Object.keys(data.items).reduce(reducer, []); console.log('final: ', results);