Reduce Method to Analyze Data

JavaScript
1 
const users = [
  { name: 'John', age: 34 },
  { name: 'Amy', age: 20 },
  { name: 'camperCat', age: 10 }
];

const usersObj = users.reduce((obj, user) => {
  obj[user.name] = user.age;
  return obj;
}, {});
console.log(usersObj);

The console would display the value { John: 34, Amy: 20, camperCat: 10 } .

Please explain me this code

2

what does confuse you?
what parts do you understand? what parts do you not understand?

3

how that reduce method return object = { John: 34, Amy: 20, camperCat: 10 }.
and working of these few lines = { obj[user.name] = user.age;
return obj;
}, {})

4

what the reeuce method returtn depends on what is returned by its callback, in this case obj, which is an object (as the starting value of the accumulator is {})
then for each element in the array a new property is added to the object with

5

but
when I put = console.log({}[users[0].name] = users[0].age); //34
it doesn’t give object

7

What do you think this line should do?

8

const users = [
{ name: ‘John’, age: 34 },
{ name: ‘Amy’, age: 20 },
{ name: ‘camperCat’, age: 10 }
];
console.log({}[users[0].name] = users[0].age) should give //John: 34

according to :-
const usersObj = users.reduce((obj, user) => {
obj[user.name] = user.age;
return obj;
}, {});

9

No.

This line is modifying obj inside of a reduce.

On this line, I’m not sure what the {} is doing, but the rest is assigning user 0’s age as user 0’s name. I’d guess that it logs 34.

How familiar are you with what reduce does? That reduce is returning obj after the callback function is called for every element in the users array.

10 
let obj = {};
obj[users[0].name] = users[0].age
console.log(obj)
11

please can you suggest me some topic to review so that I can feel this code more deeply

12

it’s object manipulation, nothing fancy or weird

1 Like
13

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