var str = '/a/:b/c/:d'
var re  = /:[a-z]+/g
var matches;

while (matches = re.exec(str)) {
   // In array form,match is now your next match..
}

您也可以在此处使用String.match()方法.

var s = '/a/:b/c/:d',m = s.match(/:[a-z]+/g);

console.log(m); //=> [ ':b',':d' ]