Trying to use 'reduce' instead of regular for loop

Question

I am trying to get the total 'stargazers_count' from a particular user's github repo. This code, using 'for' loop is working. But I would like to use 'reduce'. I am posting what I tried. Can someone point to me where I am wrong? The JSON can be viewed with this url,using your github username:

https://api.github.com/users/${your username}/repos

This is the working code using for loop:

axios.get(response.data.repos_url)
  .then((res) => {

    let starCount = 0;
    for(let i=0; i<res.data.length; i++) // find out the total number of github stars
    {
        starCount += res.data[i].stargazers_count;
    }

      response.data.NoOfStars = starCount; // add the total stars as a property in response object

This is what I tried with 'reduce':

axios.get(response.data.repos_url)
  .then((res) => {

    let starCount = 0;
    const reducer = (acc, currVal) => acc + currVal.stargazers_count;

    arr = res.data;
    starCount = arr.reduce(reducer);

This did not work. If I can get a brief explanation of where and why I am wrong, it will be helpful.

I expect it to be a number, value depends on the user, For eg. Dan Abramov, the stars count is 1427. The last time I tried.. I think I got a NaN. — Deepika
– Deepika, Commented Feb 21, 2020 at 20:03

Carsten Massmann · Accepted Answer · 2020-02-21 21:53:22Z

1

You need to provide a starting value for your accumulator, otherwise reduce will assume that the first array element is the starting value and this would lead to a NaN result.

starCount = arr.reduce(reducer,0);

answered Feb 21, 2020 at 21:53

Carsten Massmann

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