why doesn't this code work? caan anyone explain?

function getJSON(url){ const xhr = new XMLHttpRequest(); xhr.open("GET",url); xhr.onload = ()=>{ if(xhr.status===200) { let data=JSON.parse(xhr.responseText); return data; }

}

xhr.send(); }

// checkbutton console.log(

btn.addEventListener("click",()=> { var perray=getJSON(astrosUrl); console.log(perray); })