Reducing nested array - reactjs

Question

I am receiving this JSON from my backend and i need to work out the count of "concrete_compressive_cylinder_100"'s where picked_up = false
concrete_samples (can be multiple per work order) can be null ( key is always present )
sample_specimens ( 1 per concrete_sample) can be null ( key is always present )
concrete_compressive_cylinder_100 ( null to 500 per sample_specimens )
{
"uuid":"4ad7bfe1-48d6-488c-bfaf-33f7189a41d7",
"org_workorder_id":1000,
"concrete_samples":[
{
"uuid":"776a8ccb-82fd-4a42-a6eb-8f286a4a9c0b",
"workorder_uuid":"4ad7bfe1-48d6-488c-bfaf-33f7189a41d7",
"org_sample_id":5001,
"sample_specimens":{
"concrete_compressive_cylinder_100":[
{
"uuid":"b9ef3a8a-2945-41e6-a34d-d90d1bd64819",
"sample_uuid":"776a8ccb-82fd-4a42-a6eb-8f286a4a9c0b",
"picked_up":true
},
{
"uuid":"d43f15b3-2208-43de-8fff-8d237c6918f9",
"sample_uuid":"776a8ccb-82fd-4a42-a6eb-8f286a4a9c0b",
"picked_up":true
},
{
"uuid":"472f832a-6f07-4af6-97ea-e6dc7b9b3799",
"sample_uuid":"776a8ccb-82fd-4a42-a6eb-8f286a4a9c0b",
"picked_up":true
}
],
"concrete_compressive_cylinder_200":[
{
"uuid":"d659d058-e4ec-4f72-9d73-9ea98295715a",
"sample_uuid":"776a8ccb-82fd-4a42-a6eb-8f286a4a9c0b",
"picked_up":true
},
{
"uuid":"777372e0-3e58-4292-bae4-bec84dfe1402",
"sample_uuid":"776a8ccb-82fd-4a42-a6eb-8f286a4a9c0b",
"picked_up":true
},
{
"uuid":"f63f7102-7673-4e71-97e5-2d85e0c1a93d",
"sample_uuid":"776a8ccb-82fd-4a42-a6eb-8f286a4a9c0b",
"picked_up":true
}
]
}
},
{
"uuid":"61138cf3-0c49-4495-8a89-533c0a6e50bc",
"workorder_uuid":"4ad7bfe1-48d6-488c-bfaf-33f7189a41d7",
"org_sample_id":5002,
"sample_specimens":{
"concrete_compressive_cylinder_100":null,
"concrete_compressive_cylinder_200":null
}
}
]
}
I've gotten this far but it dosen't really work and now im more confused some guidance would be great
const out = res.data.concrete_samples.reduce((acc, sample) => {
const { sample_specimens } = sample;
const concrete_compressive_cylinder_100 = Object.keys(sample_specimens)["concrete_compressive_cylinder_100"];
const specimens = concrete_compressive_cylinder_100.map(obj => {
obj.picked_up ? console.log("picked up") : console.log("Not pickedn up")
});
}, []);

Answer 1

Array.prototype.reduce accepts a function whose return value is eventually returned from reduce itself. The function is passed each element of the array, along with the value accumulated so far. For example,
[1, 2, 3].reduce((accumulator, element) => accumulator + element)
// => 6
You can also provide an initial value, which will be passed to your function as accumulator on the first iteration.
At a basic level, to count how many occurrences of an object with a certain property with reduce, you could use something like this,
let array = [
{ foo: 4 },
{ foo: 6 },
{ bar: 8 },
]
array.reduce((count, element) => {
if (element.foo !== undefined) {
return count + 1
} else {
return count
}
}, 0)
// => 2
Extending this to your code (with extraneous data elided), with a nested reduce to get the count of cylinders with the desired picked_up property,
const data = {
"concrete_samples":[
{
"sample_specimens":{
"concrete_compressive_cylinder_100":[
{
"picked_up":true
},
{
"picked_up":true
},
{
"picked_up":true
}
],
"concrete_compressive_cylinder_200":[
{
"picked_up":true
},
{
"picked_up":true
},
{
"picked_up":true
}
]
}
},
{
"sample_specimens":{
"concrete_compressive_cylinder_100":null,
"concrete_compressive_cylinder_200":null
}
}
]
}
const result = data.concrete_samples.reduce((count, sample) => {
const cylinders = sample.sample_specimens.concrete_compressive_cylinder_100
if (cylinders == null) {
return count
}
const samplePickedUpCount = cylinders.reduce((pickedUpCount, cylinder) => {
if (cylinder.picked_up) {
return pickedUpCount + 1
} else {
return pickedUpCount
}
}, 0)
return count + samplePickedUpCount
}, 0)
console.log(result)
You could also use Array.prototype.filter to accomplish the same thing, getting an array of the cylinders with the desired property, and getting the length of that array.

Answer 2

If I understand correctly, you'd like to obtain a new concrete_samples array where the array values of nested sample_specimens objects are reduced to the number of items where picked_up is true - one approach to that would be as documented in the following snippet:
const data={"uuid":"4ad7bfe1-48d6-488c-bfaf-33f7189a41d7","org_workorder_id":1000,"concrete_samples":[{"uuid":"776a8ccb-82fd-4a42-a6eb-8f286a4a9c0b","workorder_uuid":"4ad7bfe1-48d6-488c-bfaf-33f7189a41d7","org_sample_id":5001,"sample_specimens":{"concrete_compressive_cylinder_100":[{"uuid":"b9ef3a8a-2945-41e6-a34d-d90d1bd64819","sample_uuid":"776a8ccb-82fd-4a42-a6eb-8f286a4a9c0b","picked_up":true},{"uuid":"d43f15b3-2208-43de-8fff-8d237c6918f9","sample_uuid":"776a8ccb-82fd-4a42-a6eb-8f286a4a9c0b","picked_up":true},{"uuid":"472f832a-6f07-4af6-97ea-e6dc7b9b3799","sample_uuid":"776a8ccb-82fd-4a42-a6eb-8f286a4a9c0b","picked_up":true}],"concrete_compressive_cylinder_200":[{"uuid":"d659d058-e4ec-4f72-9d73-9ea98295715a","sample_uuid":"776a8ccb-82fd-4a42-a6eb-8f286a4a9c0b","picked_up":true},{"uuid":"777372e0-3e58-4292-bae4-bec84dfe1402","sample_uuid":"776a8ccb-82fd-4a42-a6eb-8f286a4a9c0b","picked_up":true},{"uuid":"f63f7102-7673-4e71-97e5-2d85e0c1a93d","sample_uuid":"776a8ccb-82fd-4a42-a6eb-8f286a4a9c0b","picked_up":true}]}},{"uuid":"61138cf3-0c49-4495-8a89-533c0a6e50bc","workorder_uuid":"4ad7bfe1-48d6-488c-bfaf-33f7189a41d7","org_sample_id":5002,"sample_specimens":{"concrete_compressive_cylinder_100":null,"concrete_compressive_cylinder_200":null}}]};
const concreteSamplesResult = data.concrete_samples.map(sample => {
// Iterate each key/value entry of sample_specimens, and reduce to a new
// specimens object that contains counts of picked_up: true items in sub array
const sample_specimens = Object
.entries(sample.sample_specimens)
.reduce((specimens, entry) => {
// Calculate count of picked_up items for arr of this entry
const [key, arr] = entry;
const count = Array.isArray(arr) ?
arr.reduce((total, item) => (total + (item.picked_up ? 1 : 0)), 0) : 0;
// Add count for entry key to newly reduced sample_specimen object
return { ...specimens, [key] : count };
},{})
return { ...sample, sample_specimens };
});
console.log(concreteSamplesResult);

Answer 3

Check null > loop > check null > loop and count isn't it?
function someFunc(json) {
const { concrete_samples } = json;
if (!concrete_samples) return;
let numberOFAvailableCylinder100s = 0;
const doSomethingWithCylinder = cylinder => {
console.log(cylinder.uuid);
numberOFAvailableCylinder100s += 1;
}
concrete_samples.forEach(concrete_sample => {
const { sample_specimens } = concrete_sample;
if (!sample_specimens) return;
findAvailableCylinder100(sample_specimens, doSomethingWithCylinder);
})
console.log(`count: ${numberOFAvailableCylinder100s}`);
}
function findAvailableCylinder100(sample_specimens, callback) {
const { concrete_compressive_cylinder_100 } = sample_specimens;
if (!concrete_compressive_cylinder_100) return;
concrete_compressive_cylinder_100.forEach(cylinder => {
if (!cylinder.picked_up) callback(cylinder);
});
}
someFunc(yourJSONObject);