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supports.js
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supports.js
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/*! matchMedia() polyfill - Test a CSS media type/query in JS.
Authors & copyright (c) 2012: Scott Jehl, Paul Irish, Nicholas Zakas. Dual MIT/BSD license */
window.matchMedia = window.matchMedia || (function (doc, undefined) {
var bool,
docElem = doc.documentElement,
refNode = docElem.firstElementChild || docElem.firstChild,
// fakeBody required for <FF4 when executed in <head>
fakeBody = doc.createElement('body'),
div = doc.createElement('div');
div.id = 'mq-test-1';
div.style.cssText = "position:absolute;top:-100em";
fakeBody.appendChild(div);
return function (q) {
div.innerHTML = '­<style media="' + q + '"> #mq-test-1 { width: 42px; }</style>';
docElem.insertBefore(fakeBody, refNode);
bool = div.offsetWidth == 42;
docElem.removeChild(fakeBody);
return { matches: bool, media: q };
};
})(document);
(function () {
/**
* Setup dummy elements
*/
var dummy = document.createElement('_'),
inline = dummy.style,
style = document.createElement('style');
document.documentElement.appendChild(style);
dummy.setAttribute('data-foo', 'bar');
dummy.setAttribute('data-px', '1px');
document.documentElement.appendChild(dummy);
var _ = window.Supports = {
prefixes: ['', '-moz-', '-webkit-', '-o-', '-ms-', 'ms-', '-khtml-'],
property: function (property) {
if (property.charAt(0) === '-') {
return camelCase(property) in inline ? property : false;
}
if (!_.property.cached) {
_.property.cached = {};
}
else if (_.property.cached[property]) {
return _.property.cached[property];
}
for (var i = 0; i < _.prefixes.length; i++) {
var prefixed = _.prefixes[i] + property;
if (camelCase(prefixed) in inline) {
return _.property.cached[property] = prefixed;
}
}
return _.property.cached[property] = false;
},
value: function (property, value) {
property = _.property(property);
if (!property) { return false; }
property = camelCase(property);
inline.cssText = '';
inline[property] = '';
for (var i = 0; i < _.prefixes.length; i++) {
var prefixed = _.prefixes[i] + value;
try {
inline[property] = prefixed;
} catch (e) { }
if (inline.length > 0) {
return prefixed;
}
}
return false;
},
descriptorvalue: function (descriptor, value) {
/* doesn't handle prefixes for descriptor or value */
style.textContent = "@font-face {" + descriptor + ":" + value + "}";
try {
return style.sheet.cssRules.length == 1 &&
style.sheet.cssRules[0].style.length == 1;
} catch (e) {
return false;
}
},
selector: function (selector) {
if (!_.selector.cached) {
_.selector.cached = {};
}
else if (_.selector.cached[selector]) {
return _.selector.cached[selector];
}
for (var i = 0; i < _.prefixes.length; i++) {
var prefixed = selector.replace(/^(:+)/, '$1' + _.prefixes[i]);
try {
document.querySelector(prefixed);
return _.selector.cached[selector] = prefixed;
}
catch (e) { }
}
return _.selector.cached[selector] = false;
},
atrule: function (atrule) {
if (!_.atrule.cached) {
_.atrule.cached = {};
}
else if (_.atrule.cached[atrule]) {
return _.atrule.cached[atrule];
}
for (var i = 0; i < _.prefixes.length; i++) {
var prefixed = atrule.replace(/^@/, '@' + _.prefixes[i]);
style.textContent = prefixed + '{}'; // Safari 4 has issues with style.innerHTML
if (style.sheet.cssRules.length > 0) {
return _.atrule.cached[atrule] = prefixed;
}
}
return _.atrule.cached[atrule] = false;
},
mq: function (mq) {
if (window.matchMedia) {
return matchMedia(mq).media !== 'invalid';
}
else {
style.textContent = '@media ' + mq + '{ foo {} }';
return style.sheet.cssRules.length > 0 ? mq : false;
}
}
};
/**
* Private
*/
function camelCase(str) {
return str.replace(/-([a-z])/g, function ($0, $1) { return $1.toUpperCase(); }).replace('-', '');
}
})();