How can fire the click event button automatically

I have a download button in my page,I want to trigger it automatically when render to this page, how can I do that? I read some answers from Stack Overflow to useRef(), but I still do not quite understand how to apply it.

My download function:

const downloadHandler = async (e) => {

    const getNewCategory = async () => {
        await axios({
        method: "GET",
        url: "http://localhost:3001/download",
        headers: {
          "Content-Type": "application/json"
        }
      }).then(res => {
        setNCategory(res.data)
        console.log("res.data: "+JSON.stringify(res.data));
      });
    }

     getNewCategory()
}

My button:

<div className="field">
    <div className="control">
        <button type="button" onClick={downloadHandler} className="btn-small">
             Download
        </button>
    </div>
</div>

>Solution :

Add an id to your button

<button id="download" type="button" onClick={downloadHandler} className="btn-small">

Then you can manually trigger click event

const downloadButton = document.getElementById('download');

downloadButton.dispatchEvent(new MouseEvent('click', {
  'view': window,
  'bubbles': true,
  'cancelable': false
}));

Call it like above where you needed

UPDATE
Using ref, here’s the way

We define our ref

const downloadButton = useRef(null);

and use it on or button

<button ref={downloadButton} type="button" onClick={downloadHandler} className="btn-small">

then trigger click event

downloadButton.current.dispatchEvent(new MouseEvent('click', {
  'view': window,
  'bubbles': true,
  'cancelable': false
}));