Struggling with calling a function that uses promises in node.js

Question

I am struggling with some code... The 2 examples below I would think would work the same but the second example throws an error? I am also struggling to figure out the error, it's not bubbling up? Admittedly I am not a seasoned node developer so any guidance would be much appreciated! If it's relevant the create method in the module is calling the sequelize create.

This works

var p1 = deliverabiltyConfigs.create2(cfgObject);      
return Promise.all([p1]).then(function([res1]) {
   res.json({result: res1})    
});

This does not

deliverabiltyConfigs.create2(cfgObject).then(res1 =>{
   res.json({result: res1}) 
})

Here is the function that I am calling in a controller module

exports.create2 = (dConfig) => {    
  DeliverabilityConfig.create(dConfig)
    .then(data => {
      return data
    })
    .catch(err => {
      return {
        message:
          err.message || "Some error occurred while createing this config."
      };
    });
};

Answer 1

The create2 function always returns null, so neither invocation will work. Promise.all([p1]) hides the problem, returning a promise to perform an array of no promises.

create2(cfgObject).then(res1 =>{ attempts to invoke then() on null, generating a more obvious error. But neither way works.

Fix by deciding which promise syntax you want, using each as follows:

Using original promise syntax....

exports.create2 = dConfig => {  
  // note the return  
  return DeliverabilityConfig.create(dConfig)
  .catch(err => {
    const message = err.message || "Some error occurred while createing this config.";
    return { message };
  });
};

// caller
deliverabiltyConfigs.create2(cfgObject).then(result =>{
   res.json(result);
})

With recent syntactic sugar...

exports.create2 = async (dConfig) => {  
  try {
    // its fine to not await here, since the caller will await
    // but just to illustrate how you might perform more async work here...
    return await DeliverabilityConfig.create(dConfig);
  } catch (err) {
    const message = err.message || "Some error occurred while createing this config."
    return { message }
  }
}

// caller 
var result = await deliverabiltyConfigs.create2(cfgObject);
res.json(result);

Use Promise.all() to run >1 promise concurrently. You've only got one promise in the OP, so no reason for it here.