I managed to create a query to get some data from the database using the following script:
app.get("/diseases", async (req, res) => {
const rows = await process.postgresql.query(
"SELECT ds.disease, ds.symptom FROM diseases ds"
);
console.log(rows);
res.status(200).send(JSON.stringify(rows));
});
The data comes in the following format:
[
{ disease: ' boală hipertensivă', symptom: ' durere toracică' },
{
disease: ' boală hipertensivă',
symptom: ' respirație întretăiată'
},
{ disease: ' boală hipertensivă', symptom: ' amețeală' },
{ disease: ' boală hipertensivă', symptom: ' astenie' },
{ disease: ' boală hipertensivă', symptom: ' toamnă (Fall)' },
{ disease: ' boală hipertensivă', symptom: ' sincopă' },
{ disease: ' diabet', symptom: ' poliurie' }
]
My question is how to transform this data in a format, like the following:
{"Hypertensive disease": ["Pain chest", "Shortness of breath", "Dizziness", "Asthenia", "Fall", "Syncope", "Vertigo", "Sweat", "Sweating increased", "Palpitation", "Nausea", "Angina pectoris", "Pressure chest"], "Diabetes": ["Polyuria"]}
You're trying to group and transpose the data. The best way is to use .reduce() function on the array. Here's an example:
const arr = [
{ disease: "boală hipertensivă", symptom: " durere toracică" },
{ disease: "boală hipertensivă", symptom: " respirație întretăiată" },
{ disease: "boală hipertensivă", symptom: " amețeală" },
{ disease: "boală hipertensivă", symptom: " astenie" },
{ disease: "boală hipertensivă", symptom: " toamnă (Fall)" },
{ disease: "boală hipertensivă", symptom: " sincopă" },
{ disease: "diabet", symptom: " poliurie" }
];
console.log(arr.reduce((group, row) => {
// Check if disease group has the disease
if (typeof group[row.disease] === "undefined") {
// Initialise an array.
group[row.disease] = [];
}
// Push the symptoms.
group[row.disease].push(row.symptom.trim());
// return the updated group.
return group;
}, {}));.as-console-wrapper { max-height: 100% !important; top: 0; }For the given input above, I get this response:
{
"boală hipertensivă": [
"durere toracică",
"respirație întretăiată",
"amețeală",
"astenie",
"toamnă (Fall)",
"sincopă"
],
"diabet": [
"poliurie"
]
}
return rows.reduce((acc, item) => { if (!!acc[item.disease]) acc[item.disease].push(item.symptom); else acc[item.disease] = [item.symptom]; return acc; }, {})
The reduce function takes two parameters - an iteration processing function, which accumulates a result, and initial result (we put as initial result an empty object {} ).
The iteration processor has two params - the accumulator object acc and current item item, and it should return new (or modified) accumulator object.
On each iteration our function checks if acc already has a field with 'disease' value. If it doesnt' - it creates this field and puts 1 item array [item.symptom] inside. If the field already exists, it pushes a symptom to that array. After we process data we get the object with deseases as keys, and arrays of their symptoms as values.