Ternary conditional works one time but not another javascript

Question

First of all this does not work for me, And I explain it so that they do not close the question, I am making two more or less equal algorithms with ternary conditional, simply one is an array of objects and the other an array of numbers, and with the numbers I don't have that problem, that's why What do I think is a problem with the code: When should I use a return statement in ES6 arrow functions

I'm new to the world of javascript and when doing a reduce for an array, I want to try to count the number of times the age is equal in an array of objects whose properties are the ages.

However when I do a ternary conditional I receive that the output is undefined.

but when doing a normal if with an else if you can do the count: Code: const numbers = [ {age: 4, age2: 4}, {age: 5, age2: 6}, {age: 88, age2: 99}, {age:14, age2:14}, {age: 2, age2: 2} ];

const getCount = ( objects ) => objects.reduce((acc, el) => {
    if ( el.age === el.age2 ) {
        return acc += 1;
    }
    else {
        return acc;
    }
}, 0);

const b = getCount(numbers)
console.log(b)

Output:

But with this Code:

const numbers = [ {age: 4, age2: 4}, {age: 5, age2: 6}, {age: 88, age2: 99}, {age:14, age2:14}, {age: 2, age2: 2} ];

    const getCount = ( objects ) => objects.reduce((acc, el) => {
        el.age === el.age2 ? acc += 1 : acc;
    }, 0);
    
    const b = getCount(numbers)
    console.log(b)

Output

undefined

However, if I don't use objects and I only do the count if some element is repeated, with the same ternary conditional, this does work.

const count2 = ( objects ) => objects.reduce( (acc, el) => el === 1 ? acc += 1 : acc )
console.log(count2( [0, 1, 2, 3, 4, 5, 1, 1, 4] ))

Output

Please I do not understand what happens, what is the error

Did you read the discussion in the link that you have added in your question? — Shivam Singla, Apr 02 '21 at 17:10
It has long, comprehensive and beautiful conversation about `return` statement in arrow functions. Please read all the posts and comments in that question carefully, try those code snippets by yourself, and you won't face that problem again — Shivam Singla, Apr 02 '21 at 17:13

Tkim · Accepted Answer · 2021-04-02T17:07:36.520

0

You have forgotten to return the accumulator value :

const getCount = ( objects ) => objects.reduce((acc, el) => {
      return el.age === el.age2 ? acc += 1 : acc;
    }, 0);

You can also remove the { } and the keywork return

const getCount = ( objects ) => objects.reduce((acc, el) => el.age === el.age2 ? acc += 1 : acc, 0)

edited Apr 02 '21 at 17:07

answered Apr 02 '21 at 16:59

Tkim

350
1
8

I can't believe I forgot that – uriesputo Apr 02 '21 at 17:13
@uriesputo It's not about forgetting. There are some places where `return` is implicit and some places where it is required. Please understand those concepts. I believe "they" had provided the link for looking into before closing your previous question. Please don't blame anyone! – Shivam Singla Apr 02 '21 at 17:16

score 0 · Answer 2 · answered Apr 02 '21 at 17:06

0

Beside the missing return statement and using a block statement, you could simplifiy the function and just add the accumulator and the comparison value.

const getCount = objects => objects.reduce((acc, el) => acc + (el.age === el.age2), 0);

answered Apr 02 '21 at 17:06

Nina Scholz

376,160
25
347
392

Ternary conditional works one time but not another javascript

2 Answers2