async waterfall and promise-CodePudding

I am using async waterfall to process nested condition in request, and using express framework. But I am confused how to process data to the next function in waterfall while the data is <promise>. This promise data is a query from sequalize.

Here is the sketch

exports.getanythinghere = async function() {

  var query = "SELECT anything, here "
              "FROM anywhere WHERE ignore this query";

  return new Promise((resolve, reject) => {
    db.sequelize.query(query , {
      type: QueryTypes.SELECT    
    }).then(wth => {
      resolve(wth);
    })
  });

}


async.waterfall([
  function(callback) {
    const trying = getanythinghere (); 
    callback(null, trying); 
  },
  function(dataone, callbackt) {
    console.log("dataone is ", dataone); 
  }
], function(err, res) {
  if (err) return callback(err);
  callback(null, res);    
});//waterfall

There dataone is always dataone is Promise { <pending> }

What I am missing here. In jquery, I will do getanythinghere().done(function(){});

But I want to have it in this callback of waterfall.

I used to do this few years ago, but I forgot since too much with java and php

Any help please..

CodePudding user response：

You don't need libraries like Async anymore, mainly because Javascript now supports async/await natively.

First, this is a Promise, because you can add it .then() :

db.sequelize.query(query , {type: QueryTypes.SELECT});

Since it is a Promise, you don't need to (and shouldn't) wrap it inside another Promise, and also you can simply await it, instead of using .then()

const trying = await db.sequelize.query(query , {type: QueryTypes.SELECT});

Using await or .then() resolves the promise, and you get a value, instead of Promise { <pending> }.

Then, you can directly use trying, you don't need to pass it to another function like a waterfall.

console.log("trying is ", trying);

Finally, all your code holds in four lines :

try{
  const query = `SELECT anything, here FROM anywhere WHERE ignore this query`;
  const trying = await db.sequelize.query(query , {type: QueryTypes.SELECT});
  console.log("trying is ", trying);
} catch(err) {
  console.log(err);
}