如何编辑对象数组？

Question

I want to edit JavaScript object.

I have an JavaScript object like this

data_without_id = [
                   0: {id: 1, name: "Mary", age: null}
                   1: {id: 2, name: "Bob", age: 33}
                   2: {id: 1, name: "Kelly", age: 40}
                  ]

I want to convert this object into this

data_without_id = [
                   0: {id: 1, name: "Kelly", age: 40}
                   1: {id: 2, name: "Bob", age: 33}
                  ]

What I need to do is:

1. Group by id

2. Get latest value.

I tried using Array.prototype.reduce() , but I can't get the result I need...

Answer 1

Using the function reduce would be as follow:

The function reduce for grouping and the function Object.values for extracting the values.

 let data_without_id = [ { id: 1, name: "Mary", age: null }, { id: 2, name: "Bob", age: 33 }, { id: 1, name: "Kelly", age: 40 }], result = Object.values(data_without_id.reduce((a, {id, name, age}) => { a[id] = {id, name, age}; return a; }, Object.create(null))); console.log(result) 

 .as-console-wrapper { max-height: 100% !important; top: 0; } 

Answer 2

You could use .reduce by making the accumulator an object that has keys of the id . This way you can overwrite any previously seen objects which had the same id , and then use Object.values to get your array of objects:

 const data_without_id = [{id: 1, name: "Mary", age: null}, {id: 2, name: "Bob", age: 33}, {id: 1, name: "Kelly", age: 40}], res = Object.values(data_without_id.reduce((acc, obj) => (acc[obj.id] = obj, acc) , {})); console.log(res); 

Answer 3

You could just simply use a for/of loop to create a copy of the data where the last object with a particular id will always be the object returned in the output data. This avoids the "grouping" part of the code but still returns the correct data.

 const data_without_id = [ { id: 1, name: "Mary", age: null }, { id: 2, name: "Bob", age: 33 }, { id: 1, name: "Kelly", age: 40 } ]; function lastId(arr) { const out = []; for (let obj of arr) { // If you don't create a copy of each object the returned // data will simply be contain _references_ to the original // data. Changes in the original data will be reflected // in the returned data out[obj.id - 1] = { ...obj }; } return out; } const lastIds = lastId(data_without_id); console.log(lastIds);