'addEventListener' of null : <p>please help me with the following code, it shows "Uncaught TypeError: Cannot read property 'addEventListener' of null".</p>

<pre><code>let btn = document.getElementById("btn");

function function1(){
  let ourRequest = new XMLHttpRequest();
  ourRequest.open('GET', 'https://learnwebcode.github.io/json-example/animals-1.json');
  ourRequest.onload = function() {
  let ourData = JSON.parse(ourRequest.responseText);
  console.log(ourData[0]);
  };
  ourRequest.send();
};
btn.addEventListener("click", function1(), false);
</code></pre>

<p>i simply dont see how its null.... :/</p>

<p>thanks in advance!</p>
