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Add a working implementation of the library and a README

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Kevin MacMartin 2015-06-30 16:10:22 -04:00
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# Contain Element
A JavaScript plugin to contain an element within its parent element.
## Features
* Pure JavaScript with no dependencies
* Configures the horizontal and vertical alignment of the contained element
* Can detect the native size or have it specified at runtime
## Usage
```
window.onload = function() {
containElement({
id: 'element', // the id of the element to be contained
width: '100', // (optional) element width in pixels (unset: element width)
height: '100', // (optional) element height in pixels (unset: element height)
valign: 'top', // (optional) vertical alignment: top|bottom (unset: middle)
halign: 'left' // (optional) horizontal alignment: left|right (unset: middle)
});
};
```
## Credits
Written by [Williams New York](http://williamsnewyork.com)
### Authors
* Kevin MacMartin
## LICENSE
Licensed under the [MIT license](http://opensource.org/licenses/MIT).

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function containElement(options) {
var scaleFactor = 1;
var element = document.getElementById(options.id);
var elementWidth = options.width ? options.width : element.offsetWidth;
var elementHeight = options.height ? options.height : element.offsetHeight;
// Apply required attributes to the element and its parents if they aren't already set
if (element.style.position != 'absolute')
element.style.position = 'absolute';
if (element.parentElement.style.overflow != 'hidden')
element.parentElement.style.overflow = 'hidden';
if (element.parentElement.style.position != 'relative' && element.parentElement.style.position != 'absolute' && element.parentElement.style.position != 'fixed')
element.parentElement.style.position = 'relative';
function scaleElement() {
var parentWidth = element.parentElement.offsetWidth;
var parentHeight = element.parentElement.offsetHeight;
// Run the scale/position functionality if able to determine the document width and height
if ((parentWidth) && (parentHeight)) {
// Calculate the scale factor
if (parentWidth > ((parentHeight / (elementHeight * scaleFactor)) * (elementWidth * scaleFactor)))
scaleFactor = (parentWidth / elementWidth);
else
scaleFactor = (parentHeight / elementHeight);
// Scale the element using the scale factor
element.style.width = (elementWidth * scaleFactor) + 'px';
element.style.height = (elementHeight * scaleFactor) + 'px';
// Anchor the element horizontally to the left/middle/right
if (parentWidth < (elementWidth * scaleFactor)) {
switch(options.halign) {
case 'left':
// anchor horizontally to the left of the parent element
element.style.left = 0 + 'px';
break;
case 'right':
// anchor horizontally to the right of the parent element
element.style.left = (0 - ((elementWidth * scaleFactor) - parentWidth)) + 'px';
break;
default:
// anchor horizontally to the middle of the parent element
element.style.left = (0 - (((elementWidth * scaleFactor) - parentWidth) / 2 )) + 'px';
}
} else {
element.style.left = 0 + 'px';
}
// Anchor the element vertically to the top/middle/bottom
if ((elementHeight * scaleFactor) > parentHeight) {
switch(options.valign) {
case 'top':
// anchor vertically to the top of the parent element
element.style.top = 0 + 'px';
break;
case 'bottom':
// anchor veritcally to the bottom of the parent element
element.style.top = (0 - ((elementHeight * scaleFactor) - parentHeight)) + 'px';
break;
default:
// anchor vertically to the middle of the parent element
element.style.top = (0 - (((elementHeight * scaleFactor) - parentHeight) / 2 )) + 'px';
}
} else {
element.style.top = 0 + 'px';
}
} else {
// Try again in 30ms if the document didn't load enough to determine its width and height yet
window.setTimeout(scaleElement, 30);
}
}
// Run the scale function and bind it to various window-size-changing events
scaleElement();
window.onload = function(event) { scaleElement(); };
window.onresize = function(event) { scaleElement(); };
screen.addEventListener('orientationchange', function() { scaleElement(); });
}