I am trying to use a Sequelize promise inside of an existing async/await chain. Sequelize returns everything as a promise. I am new to promises and async/await so I am using this as something of a learning experience. Please be extra patient with me.
My logic looks like this:
if row does not exist from previous '.then'
create a new row and extract the new id
else
extract id value from previous '.then'
So now I have a WORKING block of code now (below), from studying many excellent SO examples. I want to use all anonymous functions since IMHO it makes it a little bit easier to read. (yes debatable point, but for now I want to try getting this working with anonymous functions.
It seems odd to have three nested return statements. Is there a way to rewrite this block of code to be a bit cleaner but just using anonymous functions?
yourTable.findAll( {...})
.then( (data) => {
// more code
})
.then( (data) => {
// more code
})
.then( (data) => {
if ( !Array.isArray(data) || !data.length ) {
// if record does NOT exist
return (async function () {
return await
(function () {
return new Promise( resolve => {
myTable.create( { ........ }
).then( (result) => {
resolve(result._id);
})
})
})();
})()
/* we had to create one, so we return the *NEW* _id value */
} else {
/* we found one, so we just return the pre-existing _id value */
return data[0]._id ;
}
})
.then( (data) => {
// more code
})
.then( (data) => {
Thank you all.
Drop all the unnecessary IIFE , IIAFE , the return await
and the Promise
constructor antipattern :
if (!Array.isArray(data) || !data.length) {
// if record does NOT exist
const result = await myTable.create({ ........ });
return result._id; // we had to create one, so we return the *NEW* _id value
} else {
return data[0]._id; // we found one, so we just return the pre-existing _id value
}
Promises are just values which can be await
ed but you actually don't strictly need to await
them, especially if your surrounding structure isn't using async
/ await
. You could write it like this:
yourTable.findAll({ /* ... */ })
.then((data) => {
if (!Array.isArray(data) || !data.length) {
// We need to create one, return the new ID
return myTable.create({ /* ... */ })
.then((result) => result._id)
} else {
// We found one, return the existing ID
return data[0]._id
}
})
If you return a Promise from within a .then()
it will become part of the parent chain which is probably exactly what you want.
If you really want to use async
/ await
, then I would recommend flipping the logic and doing the larger work after your happy path is accounted for like so:
yourTable.findAll({ /* ... */ })
.then(async (data) => {
if (data && data.length) return data[0]._id
const result = await myTable.create({ /* ... */ })
return result._id
})
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