jquery 常用的获取dom的方法

var Expr = Sizzle.selectors = {
	order: [ "ID", "NAME", "TAG" ],

	match: {
		ID: /#((?:[\w\u00c0-\uFFFF\-]|\\.)+)/,
		CLASS: /\.((?:[\w\u00c0-\uFFFF\-]|\\.)+)/,
		NAME: /\[name=['"]*((?:[\w\u00c0-\uFFFF\-]|\\.)+)['"]*\]/,
		ATTR: /\[\s*((?:[\w\u00c0-\uFFFF\-]|\\.)+)\s*(?:(\S?=)\s*(?:(['"])(.*?)\3|(#?(?:[\w\u00c0-\uFFFF\-]|\\.)*)|)|)\s*\]/,
		TAG: /^((?:[\w\u00c0-\uFFFF\*\-]|\\.)+)/,
		CHILD: /:(only|nth|last|first)-child(?:\(\s*(even|odd|(?:[+\-]?\d+|(?:[+\-]?\d*)?n\s*(?:[+\-]\s*\d+)?))\s*\))?/,
		POS: /:(nth|eq|gt|lt|first|last|even|odd)(?:\((\d*)\))?(?=[^\-]|$)/,
		PSEUDO: /:((?:[\w\u00c0-\uFFFF\-]|\\.)+)(?:\((['"]?)((?:\([^\)]+\)|[^\(\)]*)+)\2\))?/
	},