let str='f34rrfsdf 45tsdgsrdg 5terg56456fdghdr675 dsf3434535645645645674567';
let re=/\d+/g;

alert(str.match(re));

弹出所有的数字组成的结果,如果数字之间有空格则按两个处理 (34,45,5,6,56456,675,3434535645645645674567)