如何将序列查询的结果推送到数组

Question

I have a node.js app and I'm using sequelize and mysql for the database.

I have been looking through the sequelize and bluebird docs trying to find a way to push a sequelize query to a an array. I have an array of orders that I loop through and then do a query on the address model.

I my query looks like this:

    var objArr = [];
    models.address.findById(6).then(function(address){
      objArr.push(address);
    });
    console.log(objArr);

if I move the console.log inside the query it works, but outside objArr is empty. I'm trying to figure out why that is. Is it not possible to do this? I can't find the answer here or the docs I mentioned above. I'm willing to read more docs, if somebody could point me in the right direction

Answer 1

Your code is asynchronous, that means that your console.log is executed before your push :

var objArr = [];
models.address.findById(6).then(function(address){
  objArr.push(address);
});
console.log(objArr);  // This code is executed before the objArr.push(address);

Answer 2

It's because the callback is asynchronous... the order looks like this:

var objArr = [];

models.address.findById(6);  //makes query, starts waiting for a response

// array is empty at this point
console.log(objArr);

//at a later time got answer, invoking callback
.then(function(address){

})

This is pseudocode, just to illustrate the point. This code will not work

it's likely you're trying to do something like this:

function () {
  var objArr = [];
  models.address.findById(6).then(function(address){
    objArr.push(address);
  });
  console.log(objArr);
  return objArr
}

Instead you should handle all of this as asynchronous code. Example with an callback:

function (callback) {
  models.address.findById(6).then(function(address){
    callback(address);
  });
}

Or you should look up Promises. That's where that ".then" comes from

Answer 3

You can do something like:

var objArr = [];
models.address.findById(6).then(function(address){
  objArr.push(address);
  return objArr;
})
.then(console.log);