get element by class and addclass javascript code example

Example 1: getelementsbyclassname add class

.newclassname { color: blue; }

Example 2: getelementsbyclassname add class

.newclassname {   border: 16px solid black; /* Light grey */
  border-top: 16px solid black; /* Blue */
  border-radius: 50%;
  width: 120px;
  height: 120px;
  animation: spin 2s linear infinite; }
  @keyframes spin {
0% { transform: rotate(0deg); }
100% { transform: rotate(360deg); }
}