How to maintain a JS function after refresh?

I'm trying to implement this function:

function aumentarFont() {
document.getElementById("myP").style.fontSize = "medium";
}

Performs the action:

<a href="#" type="text" onclick="aumentarFont()">A+</a>

Apparently this is working properly, but when I refresh the page the font returns to its normal size. How do I make this function continue after the refresh?