获取公共字符串，key唯一

//获取公共字符串，key唯一
function getCST(s1,s2) {
  const arr=[];
  let start=0;
  let n1=0;
  let n2=0;
  while (n1<s1.length&&n2<s1.length){
    if(s1[n1]===s2[n2]){
      arr.push(s1[n1])
      n1=n1+1;
      n2=n2+1;
      start=n1;
    }else{
      n1++;
    }
    if(n1===s1.length){
      n1=start;
      n2++;
    }
  }
  return arr.join('')
}
console.log(getCST('姏的败','的鷉败'))