add style to a class in javascript code example

Example 1: add style javascript

// Bad:
element.setAttribute("style", "background-color: red;");
// Good:
element.style.backgroundColor = "red";

Example 2: js add style to each class

var all = document.getElementsByClassName('someClass');
for (var i = 0; i < all.length; i++) {
  all[i].style.color = 'red';
}