Herarchy query using sequelize / nodejs - node.js

Question

I am trying to load a hierarchy in my database. I have a column with parentId in my table so every row can have a parent. But I am having problems using recursion and promises.
function read (options) {
return serviceItemAttributeModel.findOne({
id: options.id,
id_organization: options.idOrganization
})
.then((attribute) => {
if (attribute) {
return loadChildren(attribute, attribute);
} else {
return attribute;
}
});
}
function loadChildren (root, attribute) {
return serviceItemAttributeModel.findAll({
where: {
id_parent: attribute.id
}
})
.then((attributes) => {
if (!attributes) {
return root;
} else {
attribute.serviceItemAttributes = [];
attributes.forEach(function (each) {
attribute.serviceItemAttributes.push(each);
return loadChildren(root, each);
});
}
});
}
So, I call read that calls loadChildren to recursively try to load all entities (by looking children of an entity) and I get an undefined value. Any ideas?
I am also getting an error on console: a promise was created in a handler but was not returned from it.
EDIT:
Came up if this solution after Nosyara help. thanks!:
function read (options) {
return serviceItemAttributeModel.findOne({
where: {
id: options.attributeId,
id_organization: options.idOrganization
}
})
.then((attribute) => {
if (!attribute) {
return new Promise(function (resolve, reject) {
resolve(attribute);
});
} else {
return new Promise(function (resolve, reject) {
attribute.queryCount = 1;
resolve(attribute);
})
.then((attribute) => loadChildren(attribute, attribute));
}
});
}
function loadChildren (root, attribute) {
return new Promise(function (resolve, reject) {
return serviceItemAttributeModel.findAll({
where: {
id_parent: attribute.id
}
})
.then((attributes) => {
attributes.length = attributes.length || 0;
root.queryCount = root.queryCount - 1 + attributes.length;
if (root.queryCount === 0) {
resolve(root);
} else if (root.queryCount > 10) {
let error = new Error('Service attribute hierarchy cant have more then 10 levels');
error.statusCode = 500;
reject(error);
} else {
attribute.serviceItemAttributes = [];
attributes.forEach(function (each) {
attribute.serviceItemAttributes.push(each);
return loadChildren(root, each).then(() => {
resolve(root);
});
});
}
});
});
}

Answer 1

You messing up with async calls and returns. You can convert both function to async, and pass through result structure to be updated. Example:
function read(...) {
return new Promise(function (accept, reject) {
// You code goes here, but instead of return
accept(resultFromAsyncFunction);
});
}
// ...
read(...).then(function(resultData) { ... });
Here is example of Promise recursion.