how to code an element style with javascript code example

Example 1: how to change css using javascript

document.getElementById("myText").className = "anyNewClass"

Example 2: how to change an element in a different elements code css

/*If the cube is directly inside the container:*/

#container:hover > #cube { background-color: yellow; }

/*If cube is next to (after containers closing tag) the container:*/

#container:hover + #cube { background-color: yellow; }

/*If the cube is somewhere inside the container:*/

#container:hover #cube { background-color: yellow; }

/*If the cube is a sibling of the container:*/

#container:hover ~ #cube { background-color: yellow; }