Get Approximate LoC

app.js

let headers = new Headers();

//headers.append('Content-Type', 'text/json');
headers.append('Authorization', 'Basic ' + btoa('username' + ":" + 'token'))

fetch('https://api.github.com/repos/username/reponame/stats/contributors', { method:'GET', headers: headers })
    .then(response => response.json())
    .then(contributors => contributors
        .map(contributor => contributor.weeks
            .reduce((lineCount, week) => lineCount + week.a - week.d, 0)))
    .then(lineCounts => lineCounts.reduce((lineTotal, lineCount) => lineTotal + lineCount))
    .then(lines => window.alert(lines));