js add css style to element

1document.getElementById("demo").style.display = "none";

1// Create our stylesheet
2var style = document.createElement('style');
3style.innerHTML =
4	'.some-element {' +
5		'color: purple;' +
6		'background-color: #e5e5e5;' +
7		'height: 150px;' +
8	'}';
9
10// Get the first script tag
11var ref = document.querySelector('script');
12
13// Insert our new styles before the first script tag
14ref.parentNode.insertBefore(style, ref);
15

1document.getElementById("myH1").style.color = "red";