contain-element/contain-element.js

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JavaScript
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function ContainElement(options) {
var scaleFactor = 1;
var element = document.getElementById(options.id);
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var elementWidth = options.width || element.offsetWidth;
var elementHeight = options.height || element.offsetHeight;
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// Apply required attributes to the element and its parents
element.style.position = 'absolute';
element.parentElement.style.overflow = 'hidden';
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if (['relative', 'absolute', 'fixed'].indexOf(window.getComputedStyle(element.parentElement, null).getPropertyValue('position')) === -1)
element.parentElement.style.position = 'relative';
function updateContain() {
var parentWidth = element.parentElement.offsetWidth;
var parentHeight = element.parentElement.offsetHeight;
// Run the scale/position functionality if able to determine the parent element's 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/center/right
if (parentWidth < (elementWidth * scaleFactor)) {
switch(options.halign) {
case 'left':
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// Anchor horizontally to the left of the parent element
element.style.left = 0 + 'px';
break;
case 'right':
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// Anchor horizontally to the right of the parent element
element.style.left = (0 - ((elementWidth * scaleFactor) - parentWidth)) + 'px';
break;
default:
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// Anchor horizontally to the center 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/center/bottom
if ((elementHeight * scaleFactor) > parentHeight) {
switch(options.valign) {
case 'top':
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// Anchor vertically to the top of the parent element
element.style.top = 0 + 'px';
break;
case 'bottom':
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// Anchor veritcally to the bottom of the parent element
element.style.top = (0 - ((elementHeight * scaleFactor) - parentHeight)) + 'px';
break;
default:
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// Anchor vertically to the center 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 the parent element's width and height yet
window.setTimeout(updateContain, 30);
}
}
// Run the function to scale and anchor the element
updateContain();
// Add an external scale and anchor update function
this.update = updateContain;
}