Get variables to JS object

$_GET.js

$_GET = (function() { 
    let x = {}; 
    (decodeURI(window.location.search).replace("?","").split("&")||[]).forEach(el=>{
        let ab = el.split("="); 
        if(ab[0].slice(-2) == "[]") { 
            ab[0]=ab[0].replace("[]","");
            if(!Array.isArray(x[ab[0]])){ x[ab[0]] = []; } 
            x[ab[0]].push(ab[1]); 
        }
        else { x[ab[0]] = ab[1] } 
    }); 
    return x;
})();