You're starting your document with <!doctype html> so you're saying you're writing HTML5, but there is a whole bunch of things that are incredibly wrong here due to use HTML3.2 and obsolete ways to invoke javascript.
Under modern HTML5 rules, there are no self-closing elements. It's not a hard error, but don't add that /> at the end of an <img.... Also <font> hasn't existed as element for 20 years now. It was removed in HTML4.1 in 1998. Then some semantics: if you need button functionality (i.e. clickable, but NOT navigating to some (part of a) page), use <button>. That's what it's for. Do not use <a>, and definitely not with href="#", because that's an active instruction for the browser to scroll to the top of the page. Finally, on...=... handlers are an ancient attribute that is unfortunately still supported, but you should never use. Use addEventListener in your Javascript, after you've declared all your HTML.
So let's just fix everything at the same time:
<!-- this line literally tells the browser "I am using HTML5" -->
<!DOCTYPE html>
<html>
<!-- always have a header section -->
<head>
<!-- no / at the end of meta elements -->
<meta charset="utf-8">
<meta name="viewport" content="width=device-width">
<title>Always just fill this in, it's good practice</title>
<style>
/* you want this in its own file, see the note at the end of this post */
h1 {
font-size: 100%;
font-weight: bold;
}
</style>
</head>
<body>
<!-- sectioning isn't mandatory, but extremely good practice -->
<section id="output">
<h1>URL Output:</h1>
<p>Forecast Hour:</p>
<div class="controls">
<!-- let's use data attributes, and be explicit about the values here -->
<button class="forecast update" data-value="0">0h</button>
<button class="forecast update" data-value="1">1h</button>
<button class="forecast update" data-value="2">2h</button>
</p>
<!-- if you've never see the figure/figcaption elements: they exist -->
<figure id="forecast-image">
<!-- no / at the end of this element -->
<img src="placeholder.jpg" width="850" height="600" alt="forecast map">
<figcaption></figcaption>
</figure>
</section>
<section>
<h1>Region Selection</h1>
<div class="controls">
<button class="area update" data-value="neast">Northeast</buton>
<button class="area update" data-value="seast">Southeast<button>
</div>
</section>
<!-- don't put your script in the page. put it in its own file -->
<script src="updates.js"></script>
</body>
</html>
And then we make a second file for the javascript called updates.js:
// this goes last, so that the DOM is done by the time you invoke your script.
var currentTime = 0;
var currentArea = `NorthEast`;
// this function doesn't need parameters: we already know what they are
function load_updated_image() {
var url = `http://personal.psu.edu/kps5442/modelimages/hrrr_${currentArea}_wetbulb${currentTime}.png`;
let figure = document.getElementById(`forecast-image`);
// update the image
let img = figure.querySelector(`img`);
img.src = url;
// update the image caption with a link
let caption = figure.querySelector(`figcaption`);
caption.innerHTML = ``;
let link = document.createElement(`a`);
link.href = url;
caption.appendChild(link);
}
// update the area, and called image update
function update_area(area) {
currentArea = area;
load_updated_image();
};
// update the time, and called image update
function update_time(time) {
currentTime = timel
load_updated_image();
};
// add the initial page load handling
document.addEventListener(`ready`, evt => load_updated_image());
// add the click handling for forecast time buttons
let forecastButtons = document.querySelectorAll(`button.forecastupdate`);
forecastButtons.forEach(button => {
// get the button's data-value
value = button.dataset.value;
// and then set up a click listener to update the forecast time
button.addEventListener(`click`, evt => update_time(value));
});
// add the click handling for forecast area buttons
let areaButtons = document.querySelectorAll(`button.area.update`);
forecastButtons.forEach(button => {
// get the button's data-value
value = button.dataset.value;
// and then set up a click listener to update the forecast area
button.addEventListener(`click`, evt => update_area(value));
});
And then to be even more proper, don't use <style>...</style> but make a new file called "forecast.css" and then link to that in your page using <link href="forecast.css" rel="stylresheet"> (note: this is still HTML5, you don't put /> at the end. Link elements simply don't have a closing tag)
/>at the end of an<img, also<font>hasn't existed as element since 1998. Also, if you need click functionality, use<button>, not<a>, and definitely not withhref="#", which is an active instruction to scroll the document to the top. Finally,on...handlers are also legacy JS, so you want to useaddEventListerin your javascript, after you've declared all your HTML.