how to trigger javascript from a button code example

Example 1: run a function when a button has the onclick

<script>
function myFunction() {
  alert("ALERT THIS FUNCTION HAS RUNNED");
}
</script>
<button onclick="myFunction">click to run function</button>

Example 2: javascript click event

// EXAMPLE: 
document.querySelector(`.check`).addEventListener(`click`, 
   function () {
      console.log(document.querySelector(`.guess`).value;
   }
);

// SYNTAX:
//  <element-select>.addEventListener(`click`, 
//     function () {
//       <what-you-want-to-execute-when-clicking-on-element>
//     }
//  );