JavaScript get current style

<div id="box" class="box">
    sss
</div>

Use external style file 1.css:

*{
    margin: 0;
    padding: 0;
}


.box{
    width: 320px;
    background: #f00;
    transform:translateX(30px);
}

JS get the current style method:

let getStyle = function(tag,prop){
    return tag.currentStyle? tag.currentStyle[prop] : getComputedStyle(tag)[prop] ;
};

let box = document.getElementById("box");
console.info( getStyle(box,"width"));   // 320px