javascript正则表达式分组-捕获性分组/非捕获性分组/正则前瞻

var data = 'windows 98 is ok';
data.match(/windows (?=\d+)/);  // ["windows "]
data.match(/windows (?:\d+)/);  // ["windows 98"]
data.match(/windows (\d+)/);    // ["windows 98", "98"]

var str_img = "img1.jpg,img2.jpg,img3.bmp";
var reg = /(?:\w*)(?=\.jpg)/g;
var arr_m = str_img.match(reg);//arr_m = [ 'img1', '', 'img2', '' ]
var reg2 = /(?:\w*)(?:\.jpg)/g;
var arr_m2=str_img.match(reg2); //arr_m2=[ 'img1.jpg', 'img2.jpg' ]