I have been trying to modify grid-template-areas with javascript. I found a property in the css properties list (elem.style) in the DOM called:
grid-template-areas
elem.style
just change to elem.style.gridTemplateAreas ='"z z z" "a b c" "d e f"';
elem.style.gridTemplateAreas ='"z z z" "a b c" "d e f"';