Correct way to write loops for promise.

Question

How to correctly construct a loop to make sure the following promise call and the chained logger.log(res) runs synchronously through iteration? (bluebird)

db.getUser(email).then(function(res) { logger.log(res); }); // this is a promise

I tried the following way (method from http://blog.victorquinn.com/javascript-promise-while-loop )

var Promise = require('bluebird');

var promiseWhile = function(condition, action) {
    var resolver = Promise.defer();

    var loop = function() {
        if (!condition()) return resolver.resolve();
        return Promise.cast(action())
            .then(loop)
            .catch(resolver.reject);
    };

    process.nextTick(loop);

    return resolver.promise;
});

var count = 0;
promiseWhile(function() {
    return count < 10;
}, function() {
    return new Promise(function(resolve, reject) {
        db.getUser(email)
          .then(function(res) { 
              logger.log(res); 
              count++;
              resolve();
          });
    }); 
}).then(function() {
    console.log('all done');
}); 

Although it seems to work, but I don't think it guarantees the order of calling logger.log(res);

Any suggestions?

Answer 1

Use async and await (es6):

function taskAsync(paramets){
 return new Promise((reslove,reject)=>{
 //your logic after reslove(respoce) or reject(error)
})
}

async function fName(){
let arry=['list of items'];
  for(var i=0;i<arry.length;i++){
   let result=await(taskAsync('parameters'));
}

}