[英]How to count the number of objects in the table
How can I get count of objects in the table.如何获取表中对象的数量。 I want all objects looks like the same.我希望所有对象看起来都一样。 Eg in element "b" I don't have any objects, but in output I want to get all used objects with count 0.例如,在元素“b”中,我没有任何对象,但在 output 中,我想获取计数为 0 的所有已使用对象。
INPUT DATA
{
a: {
obj3: [{...}, {...}]
},
b: { },
c: {
obj1: [{...}, {...}, {...}]
obj2: [{...}, {...}]
}
}
OUTPUT DATA
{
a: {
obj1: 0,
obj2: 0,
obj3: 2
},
b: {
obj1: 0,
obj2: 0,
obj3: 0
},
c: {
obj1: 3
obj2: 2,
obj3: 0
}
}
You can do something like this only if you want specific number of objX
as output and the key name is in the same format.仅当您希望特定数量的objX
为 output 并且密钥名称的格式相同时,您才能执行此类操作。
let input = { a: { obj3: [{x:1}, {x:2}] }, b: { }, c: { obj1: [{x:1}, {x:2}, {x:3}], obj2: [{x:1}, {x:2}] } } let output = {}; for (const [key, value] of Object.entries(input)) { let result = {} for (let i = 1; i < 4; i++) { result['obj'+i] = value['obj'+i]? value['obj'+i].length: 0; } output[key] = result; } console.log(output);
To keep the code generic and a bit easier to manage and understand, I would loop over your data twice: first to discover all the unique keys you need to handle, and second to fill the structure with the right data.为了使代码保持通用并更易于管理和理解,我将循环遍历您的数据两次:首先发现您需要处理的所有唯一键,然后用正确的数据填充结构。
To get the right keys, I look at the values of the input object (we can ignore the a
, b
and c
keys).为了获得正确的键,我查看了输入 object 的值(我们可以忽略a
、 b
和c
键)。
We're interested in all keys of the objects in this layer.我们对这一层中对象的所有键感兴趣。 We can create a flat list of them using flatMap(Object.keys)
.我们可以使用flatMap(Object.keys)
创建它们的平面列表。
Because this list might contain duplicate keys, I store them in a Set
.因为这个列表可能包含重复的键,所以我将它们存储在Set
中。 This ensures all keys appear only once.这确保所有键只出现一次。 With the example data you provided, we now have a Set
of "obj1", "obj2", "obj3"
.使用您提供的示例数据,我们现在有一Set
"obj1", "obj2", "obj3"
。
We can now transform any object to an object that has all keys.我们现在可以将任何 object 转换为具有所有键的 object。 I capture this transformation in a Result
constructor function.我在Result
构造函数 function 中捕获了这种转换。
This function creates a list of all keys ( [...allKeys]
), map
s over them, and checks our input object for the existence of the key (obj[k]?
).这个 function 创建了一个所有键的列表( [...allKeys]
), map
s 在它们之上,并检查我们的输入 object 是否存在键(obj[k]?
) If the key exists, we use its length.如果密钥存在,我们使用它的长度。 If not, we default to 0
.如果没有,我们默认为0
。
To transform your whole object, I defined a mapObj
helper.为了转换你的整个 object,我定义了一个mapObj
助手。 This takes an object, applies a function to each of its values, and returns those in a new object with the same keys.这需要一个 object,将 function 应用于其每个值,并使用相同的键返回新的 object 中的值。
const input = { a: { obj3: [{}, {}] }, b: { }, c: { obj1: [{}, {}, {}], obj2: [{}, {}] } }; // Set(3) {"obj1", "obj2", "obj3"} const allKeys = new Set( Object.values(input).flatMap(Object.keys) ); const Result = obj => Object.fromEntries( [...allKeys].map( (k) => [ k, obj[k]?.length || 0 ] ) ); console.log( mapObj(Result, input) ) // Utils function mapObj(f, o) { return Object.fromEntries( Object.entries(o).map( ([k, v]) => [k, f(v)] ) ) }
This is my solution:这是我的解决方案:
let input = { a: { obj3: [{x:1}, {x:2}] }, b: {}, c: { obj1: [{x:3}, {x:5}, {x:6}], obj2: [{x:7}, {x:8}] } } let output={}; Object.keys(input).forEach(key=>{ let item={obj1:0,obj2:0,obj3:0}; ["obj1","obj2","obj3"].forEach(itemType=>{ if (input[key][itemType]){ item[itemType]= input[key][itemType].length; } }) output[key]=item; }); console.log(output);
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