Gets the value of a GET argument (URL parameter). Returns undefined if the argument doesn't exist. Like the $_GET superglobal array in PHP.

_GET.js

/**
 * Gets the value of a GET argument (URL parameter). Returns undefined if the argument doesn't exist
 *
 * @param name string
 * @returns string|undefined
 * 
 * @author adam-lynch
 */
function _GET( name ){
  var regexS = "[\\?&]" + name.replace( /[\[]/, "\\\[" ).replace( /[\]]/, "\\\]" ) + "=([^&#]*)",
		results = (new RegExp( regexS )).exec( window.location.search );

	return results && decodeURIComponent( results[1].replace( /\+/g, " " ) ) || undefined;
}