node.js - How to make node js api synchronous to fire mongodb's multiple queries? -


i have api in node.js find id of category name , when result comes send id in function , calls of parent categories id.if there no parent category in array should added , if there parent category should added in array.my problem response send blank array because of asynchronous call.how make synchronous through async-waterfall ?please me .thank in advance

    router.post('/api/getproductofcategory', function(req, res) {       var name = req.body.category;       var cidarray = [];        category.getcategoryidbyname(name, function(err, categoryid) {         if (err) {           throw err;         }          if (categoryid.length) {           console.log(categoryid);           category.getcategorywithsameparentfun(categoryid[0]._id, function(             err,             categorywithsameparent           ) {             if (err) {               throw err;             } else {               console.log(categorywithsameparent);               if (categorywithsameparent.length == 0) {                 cidarray.push(categoryid[0]._id);               } else {                 cidarray.push(categorywithsameparent._id);               }  product.getproductbycategoryid(cidarray[0], function(err, products){                 if(err){                     console.log('error', err);                 }                 else{                     console.log(products);                             }               }) }           });         }       });        res.end('result', cidarray);     });

i changed variable names bit , made comments. don't know why want send cidarray api response anyway how control flow async/each.

const each = require('async/each');  router.post('/api/getproductofcategory', function(req, res) {   var name = req.body.category;   var cidarray = [];    category.getcategoryidbyname(name, function(err, categoryids) {     if (err) {       throw err;     }      each(       categoryids,       function(categoryid, callback) {         category.getcategorywithsameparentfun(categoryid._id, function(           err,           categorywithsameparent         ) {           if (err) {             throw err;           } else {             if (categorywithsameparent.length == 0) {               cidarray.push(categoryid[0]._id);             } else {               cidarray.push(categorywithsameparent._id);             }             callback();           }         });       },       function(err) {         // here cid array filled desired values.          each(           cidarray,           function(cid, callback) {             product.getproductbycategoryid(cid, function(err, products) {               if (err) {                 console.log('error', err);               } else {                 // don't know you're trying products here.                 // whatever should call callback() after job each cid.                 console.log(products);               }             });           },           function(err) {             // final step. end response here.             res.end('result', cidarray);           }         );       }     );   }); });

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