Function testContext

jquery.js:598–600

* Checks a node for validity as a jQuery selector context * @param {Element|Object=} context * @returns {Element|Object|Boolean} The input node if acceptable, otherwise a falsy value

( context )

 * @returns {Element|Object|Boolean} The input node if acceptable, otherwise a falsy value
 */
function testContext( context ) {
	return context && typeof context.getElementsByTagName !== "undefined" && context;
}

// Attribute selectors: https://www.w3.org/TR/selectors/#attribute-selectors
var attributes = "\\[" + whitespace + "*(" + identifier + ")(?:" + whitespace +