I want to render HTML to show as a div at 100vh but the website I am embedding on has a header, so 100vh bleeds into the header. Is there a way with JS to calculate the size of a DOM object and use that to modify the height dynamically?
user
Absolutely, you can use JavaScript's `offsetHeight` property to calculate the height of a DOM element, accounting for padding, border, and margin. Here's an example:

HTML:

```html
<header>
  <!-- your header content here -->
</header>

<div id="container"></div>

<script>
  // Your JavaScript code here
</script>
```

JavaScript:

```javascript
const container = document.getElementById('container');

// Wait for the header height to be calculated
window.addEventListener('load', function() {
  const headerHeight = document.querySelector('header').offsetHeight;

  // Update container's height dynamically
  container.style.height = (window.innerHeight || document.documentElement.clientHeight) - headerHeight + 'px';
});
```

In this code, `querySelector` returns the first element in the document that matches the selector. In this case, it's selecting the first `header` element. `offsetHeight` returns the distance between the top of the element's content area and the top side of its padding box, including border and margin.

We then calculate the height of the container by subtracting the height of the header from the viewport height or the document's visible client height.

Note: This is a rough example. You might need to adjust the CSS or Beautify it for best practices.
assistant
I want to render HTML to show as a div at 100vh but the website I am embedding on has a header, so 100vh bleeds into the header. Is there a way with JS to calculate the size of a DOM object and use that to modify the height dynamically?
user
Yes, you can use JavaScript to calculate the height of a DOM object and adjust the height of your div dynamically. Here's a simple way to do it:

1. First, get the height of the header. You can do this using the `offsetHeight` property of the header DOM object.

```javascript
var headerHeight = document.querySelector('header').offsetHeight;
```

2. Next, calculate the height of the viewport and subtract the height of the header. The `window.innerHeight` property can be used to get the height of the viewport.

```javascript
var viewportHeight = window.innerHeight;
var divHeight = viewportHeight - headerHeight;
```

3. Finally, set the height of your div to the calculated height. You can do this using the `style` property of the div DOM object.

```javascript
document.querySelector('#yourDiv').style.height = divHeight + 'px';
```

Remember to replace `'header'` and `'#yourDiv'` with the appropriate selectors for your header and div.

Also, you might want to add an event listener for the window `resize` event to recalculate and adjust the div height when the window size changes:

```javascript
window.addEventListener('resize', function() {
    viewportHeight = window.innerHeight;
    divHeight = viewportHeight - headerHeight;
    document.querySelector('#yourDiv').style.height = divHeight + 'px';
});
```

This way, your div height will always be the viewport height minus the height of the header, even when the window is resized.
assistant