How to change CSS using javascript

1

i want to change the font-size of grid row number using javascript. the font-size in the following css is used for row numbers. how can i access it using JS?

.x-grid3-td-numberer div {
font-size: 11px;
font-family: “segoe ui”, tahoma, arial, sans-serif;
color: #444444;
padding: 3px 0px 0 5px !important;
}