I'm trying to get data from an API, but I can't get outside result from the .then.

function getChampionMasteryData(championId, summonerName) {  
    var championMasteryData;
    var summonerId = process.env.SUMMONER_ID;

    axios.get(`https://euw1.api.riotgames.com/lol/champion-mastery/v4/champion-masteries/by-summoner/${summonerId}/by-champion/${championId}?api_key=${process.env.API_KEY}`, {responseType: 'json'})
        .then(result => {championMasteryData = result.data})
        .catch(e => console.log(e));

    console.log(championMasteryData);
    return championMasteryData;
}

output:

undefined