How to exclude from foreach an array that does not contain an object? - node.js

Question

I'm receiving an array and performing a treatment to extract some information.
When I get the matrix like this, everything goes well!
[
{
averages: [
[Object], [Object],
[Object], [Object],
[Object], [Object],
[Object]
]
},
{
averages: [
[Object], [Object],
[Object], [Object],
[Object], [Object],
[Object]
]
},
{
averages: [
[Object], [Object],
[Object], [Object],
[Object], [Object],
[Object], [Object]
]
},
{
averages: [
[Object], [Object],
[Object], [Object],
[Object], [Object],
[Object], [Object]
]
}
]
But when the array comes like this:
[
{
averages: [
[Object], [Object],
[Object], [Object],
[Object], [Object],
[Object]
]
},
{
averages: [
[Object], [Object],
[Object], [Object],
[Object], [Object],
[Object]
]
},
{
averages: [
[Object], [Object],
[Object], [Object],
[Object], [Object],
[Object]
]
},
{ averages: 'No data in period.' }
]
I get this error:
ccs.medias.forEach is not a function
Could this be the error?
{ averages: 'No data in period.' }
The code mentioned to filter the information I want is this:
function test(arr) {
let results = [];
arr.forEach(ccs => {
ccs.medias.forEach(element => {
if (element["TYPE"] === 'AAA') {
results.push(element["STATUS"])
}
})
})
return results;
}
As I mentioned above, this code works for the first array example, but not for the following one.
I appreciate if anyone can help me analyze it!

Answer 1

Yep, you guessed right, problem is here:
{ averages: 'No data in period.' }
Before using .forEach(), you need to make sure property value (ccs.averages) is array, so just add simple if-condition like:
if (Array.isArray(ccs.averages)) {
// Do what you need with array and only
}
Full code:
const arr = [
{
averages: [
[Object], [Object],
[Object], [Object],
[Object], [Object],
[Object]
]
},
{
averages: [
[Object], [Object],
[Object], [Object],
[Object], [Object],
[Object]
]
},
{
averages: [
[Object], [Object],
[Object], [Object],
[Object], [Object],
[Object]
]
},
{ averages: 'No data in period.' }
]
function test(arr) {
let results = [];
arr.forEach(ccs => {
// Make sure .avarages is array
if (Array.isArray(ccs.averages)) {
ccs.averages.forEach(element => {
if (element["TYPE"] === 'AAA') {
results.push(element["STATUS"])
}
})
}
})
return results;
}
console.log(test(arr));
Refs: Array.isArray().

Answer 2

As this question is tagged as "mongo", to do it in a query and retrieve results directly without the fields which are not an array you can use one of these queries:
For a find query you can add:
"averages": { "$type": "array }
Like this:
db.collection.find({
"averages": {
"$type": "array"
}
})
Example here
Also if you are using an aggregation stage you can add a $match stage like this:
db.collection.aggregate([
{
"$match": {
"averages": {
"$type": "array"
}
}
}
])
Example here
Note that the queries use $type
In this way you can avoid the loop.