W3.JS Add Style to HTML
Add a CSS property value:
w3.addStyle(selector,'property','value')
Add Style by Id
Add a red background color to an element with id="London":
Example
<button onclick="w3.addStyle('#London','background-color','red')">Add Style</button>
Add Style by Tag
Add a red background color to all <h2> elements:
Example
<button onclick="w3.addStyle('h2','background-color','red')">Add Style</button>
Add Style by Class
Add a red background color to all elements with class="city":
Example
<button onclick="w3.addStyle('.city','background-color','red')">Add Style</button>