Question

我想执行一个从DB检索数据的递归函数。在php中，下面的代码运行时只有15毫秒的魅力，可以运行

function GetSubCategories($catno,&$subcats, $useactive=true){
   global $dbconn;

   $qid = new SSQL($dbconn, "SELECT categoryno FROM article_category WHERE parent = '$catno'".($useactive?" AND active = 'Y'":"")." ORDER BY sortorder");
   if ($qid->query()){
      while($catrow=$qid->fetch_array()){
        $subcats[]=$catrow["categoryno"];
        GetSubCategories($catrow["categoryno"],$subcats, $useactive);
      }
    }

}

我是Node.js环境中的新手，在这种情况下，异步会引起麻烦。如果我在js中写相同的coe，程序将在第一次迭代后退出。我可以将流程与await保持同步，但是执行时间会激增...

我尝试很多有希望的事情

var getSubcategoriestest = function(categoryno,subcats, useactive=true){
return new Promise(async function (resolve) {
    const query = `SELECT categoryno FROM article_category WHERE ?? = ? ${useactive?" AND active = 'Y'":""} ORDER BY sortorder`
    let rows = await mysqlConn.query(query,['parent',categoryno])
    resolve(rows)
}).then((rows)=>{
    for (row of rows){
        console.log(row.categoryno)
        return new Promise(async function (resolve) {
            await getSubcategoriestest(row.categoryno,subcats, useactive)
            resolve()
        }).then(()=>{console.log('end')})
    } 
})

}

但没有任何效果

任何一位上师都可以帮助我吗？

谢谢

杰里米

我测试此代码

var getSubcategoriestest = async function(categoryno,subcats, useactive=true,arrPromise=[]){

let promise = new Promise(function (resolve,reject) {
    const query = `SELECT categoryno FROM article_category WHERE ?? = ? ${useactive?" AND active = 'Y'":""} ORDER BY sortorder`
    mysqlConn.query(query,['parent',categoryno]).then((rows)=>resolve(rows)).catch(err=>console.log(err))
}).then((rows)=>{
        for (row of rows){
            getSubcategoriestest(row.categoryno,subcats, useactive,arrPromise).then((rows)=>{subcats.push(row.categoryno)})
        }
        return row.categoryno

}) 

arrPromise.push(promise)

Promise.all(arrPromise).then(function() {
    console.log("promise all,") 
    return 
}).catch(err=>console.log(err))

}

但是函数总是在第一次迭代后结束。 Promise.all多次调用（我想是因为每次迭代都绑定）...头痛，头痛，头痛

Answer 1

我们在这里

var getSubcategoriestest = function (categoryno,subcats) {

   const query = `SELECT c FROM ac WHERE ?? = ? ORDER BY sortorder`

   return mysqlConn.query(query,['parent',categoryno]).then(rows => {   
        return Promise.all(rows.map(row => {
            subcats.push(row.categoryno);
            return getSubcategoriestest(row.categoryno, subcats,useactive);
        }));
   })}

rows.map制作了一个诺言数组，导致getSubcategoriestest返回一个诺言。您可以添加一个after after promise.all。

递归nodejs mysql查询

1 个答案: