求最长相同子序列

//求最长相同子序列
function dp(s1,s2) {
    var n=s1.length,m=s2.length;//长度
    var cs=‘‘;
    var n1=0,n2=0;//扫描点
    var chunkArr=[]
//开始扫描
    while (n1<n&&n2<m){
        //相等
        if(s1[n1]===s2[n2]){
            let nn1=n1+1;
            let nn2=n2+1;
            while (nn1<n&&nn2<m&&s1[nn1]===s2[nn2]){
                nn1++;
                nn2++;
            }
            cs=cs+s1.substr(n1,nn1-n1)
            chunkArr.push([‘e‘,n1,nn1-n1])
            n1=nn1;
            n2=nn2;
        }else{
            let d1=0;
            let d2=0;
            if(n1+1<n){
                d2=1;
            }
            if(n2+1<m){
                d1=1;
            }
            if(d1===1&&d2===1){
                if(s1[n1+1]!==s2[n2+1]){
                    while (n2+d1<m&&s1[n1]!==s2[n2+d1]){
                        d1++;
                    }
                    while (n1+d2<n&&s1[n1+d2]!==s2[n2]){
                        d2++;
                    }
                }
            }

            if(d1===d2&&n-n1===m-n2){
                //替换
                n1=n1+1;
                n2=n2+1;
            }else if(d1<d2||n-n1<m-n2){
                //增加
                n2=n2+1;
            }else{
                //删除
                n1=n1+1;
            }
        }
    }
    return cs;
}
console.log(dp(‘252434343232‘,‘2234343‘))