run reduce , map function

Asked Apr 19 '20 at 09:33

Active Apr 19 '20 at 09:45

Viewed 37 times

I have 3 classes and data in country.json

country.json

[{"country":"Algeria","region":"Northern Africa","code":"DZ","population":41318142,"cities":["Boumerdas","Zeribet el Oued","Zeralda"]},{"country":"American Samoa","region":"Polynesia","code":"AS","population":55641,"cities":["Aūa","Vaitogi","Vailoatai"]}

in countryRep class I make this funnction to get the sum of population

   async  getSumAllPopulation(){
            let countries = await this.getCountries();
           let populations= countries.map(s=>s.population).reduce((acc, s) => s + acc);
           return populations;
        }

in test I write

app.get('/PopulationSum', async (req, res) => {
    const countries = await repo.getSumAllPopulation();
    res.send(countries);
})

getCountries() function

    async getCountries() {
        try {
            const countries = await fs.readJSON(this.countryFilePath);
            return countries;
        }
        catch (e) {
            console.log(e)
        }

    }

But I didn't get the result of the sum ? How I can fix it? I got an error it seems the method didn't return any thing.

edited Apr 19 '20 at 09:45

asked Apr 19 '20 at 09:33

Duaa Aljamal

1

It is maybe because you forgot to run reduce with an initial value: `reduce((acc, s) => s + acc, 0)` – MorKadosh Apr 19 '20 at 09:36
same problem, I try it before. – Duaa Aljamal Apr 19 '20 at 09:38
2

@MorKadosh Default is 0 – Anurag Srivastava Apr 19 '20 at 09:39
What is the error you get? Post that in the question – Anurag Srivastava Apr 19 '20 at 09:39
@AnuragSrivastava just learned something new. :) – MorKadosh Apr 19 '20 at 09:41
The code itself related to `.map()` and `.reduce()` looks good to me. What do you have in `getCountries` function? How do you resolve the `Promise` inside? From the error it seems an error occurred there. – norbitrial Apr 19 '20 at 09:42
@AnuragSrivastava you can check it , I post the error – Duaa Aljamal Apr 19 '20 at 09:43
@norbitrial I post the function – Duaa Aljamal Apr 19 '20 at 09:46
1

Issue is that you send a number in res.send, which is interpreted as a response code, use string or object – Anurag Srivastava Apr 19 '20 at 09:46
@norbitrial Its work yes . thank you – Duaa Aljamal Apr 19 '20 at 09:52
@AnuragSrivastava yah I solve it. thank you – Duaa Aljamal Apr 19 '20 at 09:52

run reduce , map function

0 Answers0