var src="images/off_1.png";弹出值为:offvar src="images/off_1.png";弹出值为:offvar src="images/off_1.png";弹出值依次为:-1,0,3var src="images/off_1.png";弹出值依次为:6,15

js中substr,substring,indexOf,lastIndexOf的用法小结