正则表达式从字符串中提取两个带空格的数字

let strs = ["Something1\sth2\n649 sth\n670 sth x","Sth1\n\something2\n42 036 sth\n42 896 sth y"]

let extractNumbers = str => {
  return str.match(/\n\d+(?: \d+)?/g).map(m => m.replace(/\s+/g,''))
}

strs.forEach(str=> console.log(extractNumbers(str)))

var str1 = "Something1\sth2\n649 sth\n670 sth x";
var str2 = "Sth1\n\something2\n42 036 sth\n42 896 sth y";
var reg = /(?<=\n)(\d+)(?: (\d+))?/g;
var d;
while(d = reg.exec(str1)){
    console.log(d[2] ? d[1]+d[2] : d[1]);
}
console.log("****************************");
while(d = reg.exec(str2)){
    console.log(d[2] ? d[1]+d[2] : d[1]);
}