how to get the rotation info of a div into a variable in js

var schakkel = document.getElementById('schakkelaar').style.transform;
if (90 < schakkel && schakkel < 140){
    console.log('it workssss');


}

ey everyone, i have a question about this code. i am making a simple js game, i need to get the rotation info of a image, so when you rotate the image in that game then something needs to happen when the image is being rotated between 90 and 140 degrees. But it keeps saying that the result is null, can anybody help me? i searched everywhere on the internet but i didn't found an answer,