Invoking W3Schools CodeColor library on multiple elements

I want to offer code examples and I am using a JS code highlighter with an ID. See this URL for the working demo: https://www.w3schools.com/howto/tryit.asp?filename=tryhow_syntax_highlight

I want to use this for multiple examples but the ID only works once. I have tried both ID and Class but this still doesn’t work.

w3CodeColor(document.getElementById("myDiv")); // only works for 1 element
w3CodeColor(document.getElementByClassName("myDiv")); // does not work

The example code what I have tried is below,

<div class="myDiv">code example goes here</div>

<div id="myDiv">code example goes here</div>

Any help would be much appreciated, thanks