javascript: backgroundColor not working on a element

im trying to change the background color of this <li> element but I’m getting error Uncaught TypeError: Cannot set properties of undefined (setting 'backgroundColor'). i have been trying to fix this for hours but nothing works. As you can see, I want it to change the background color of the rows element in an if statement and below is my JS code.

var vals;
var rows;
var sum;
var rowsarr = [];
var avg;

function obser1() {
    const trades = document.querySelector('.scrollbar-dark');
    const observer = new MutationObserver(function (mutations) {
        mutations.forEach(function (mutation) {
            if (mutation.addedNodes.length) {
                vals = [...mutation.addedNodes[0].querySelectorAll("span")].map(span => span.textContent);
                if (vals.length == 4) {
                    rows = vals[2];
                    rowsarr.push(rows);
                }
                if (vals.length == 3) {
                    rows = vals[1];
                    rowsarr.push(rows);
                }
                console.log(mutation.addedNodes[0]);
                console.log(rows+"  rows");
            }
        })
        function arraysum(x, y) {
            return parseFloat(x) + parseFloat(y);
        }
        sum = rowsarr.reduce(arraysum);
        console.log(rowsarr.length + "  length");
        if (rowsarr.length >= 100 && rowsarr.length<105) {
            avg = sum / 50;
            console.log("average is  " + avg);
        }
        /*This is the problem*/
        if (rows > avg) {
            console.log(rows + "  large" + "  average  " + avg);

            rows.style.backgroundColor = "white";
        }
    });
    observer.observe(trades, {
        childList: true,
        subtree: true,
        attributes: true,
        characterData: true
    })
   
}

window.setTimeout(btn4, 1000);
window.setTimeout(obser1, 1700);