I am pushing the promises in promises =[] array but when passing the promises in promises. All the array remains null which resolves and send null result if my code has any issue please answer
searchProductVariant: (start, end, combinations) => {
return new Promise((resolve,reject)=>
{
var promises = [];
console.log(start, " ", end);
for (let i = start; i < start + end; i++) {
vv = combinations[i - start].product_variant_name.split("_");
console.log("kk", vv);
vv.forEach((v) => {
sql = `SELECT id FROM ecommerce.variant_values as varval where varval.value like '${v}'`;
pool.query(sql, [], (error, results, fields) => {
if (error) {
console.log("the errrror is", error);
}
if (results[0].id) {
console.log("i is ", i);
let temp = addProductVariantDetails(i, results[0].id);
promises.push(temp
);
}
});
});
}
console.log(promises); //it prints null
return Promise.all(promises)
.then((resul) => {
return resolve(resul);
})
.catch((err) => {
return reject(err);
});
})
}
pool.query
receives a callback, and that's the only thing that adds to the promises
array. I think it's likely that you're just trying to run Promise.all
before any of the query
callbacks return. You might need to switch to a Promise-based version of pool.query
, if one exists, or you can write your own like this.
searchProductVariant: (start, end, combinations) => {
// DELETE: Original Promise wrapper. Return Promise.all result directly.
var queries = []; // NEW: Track queries.
var promises = [];
console.log(start, " ", end);
for (let i = start; i < start + end; i++) {
vv = combinations[i - start].product_variant_name.split("_");
console.log("kk", vv);
vv.forEach((v) => {
sql = `SELECT id FROM ecommerce.variant_values as varval where varval.value like '${v}'`;
// NEW: Wrap pool.query to create a promise that waits for the possible add
// to the promises array, adding the separate promises array.
queries.push(
new Promise((resolve, _) => {
pool.query(sql, [], (error, results, fields) => {
resolve([error, results, fields]);
})
}).then([error, results, fields] => {
if (error) {
console.log("the error is", error);
}
if (results[0].id) {
console.log("i is ", i);
let temp = addProductVariantDetails(i, results[0].id);
// Keep temp in an array so we only return valid results,
// but also return it so the returned Promise surfaces
// any rejection issued at any time.
promises.push(temp);
return temp;
}
}));
});
}
console.log(promises);
// Wait for the queries, then wait for the promise results.
return Promise.all(queries).then(() => Promise.all(promises));
}
You could also simplify this code by dropping the promises
array entirely and simply returning Promise.all(queries)
at the end; however, you'd need to filter out the undefined
results that come from any queries
promises that result in errors or ID-less results, and I don't know enough about your code to know whether undefined
can be properly filtered. (You also don't check that results.length > 0
, but as you have it that would result in a Promise rejection either way.)