Is it possible to create a nested object inside of an array?

Question

Is it possible to create a nested object inside of an array?

Looking to accomplish the following:

let listOne: any = ['item1', 'item2', 'item3'];
let details: any;

// Previously, I had a loop running and 'row' was the response outputting items 
// in the listOne array

const query_for_details = `SELECT column1 FROM tableName WHERE itemId = '${row}'`;
details = await client.query(query_for_details).then((res: any) => res.rows
console.log(details)
// Output for each item in the listOne array {name1: value1, name2: value2, name3:value3}

Now, after obtaining the query output, I aim to store it in a new variable like shown below:

let listOneDetails: any = [{'item1': {'name1': 'value1', 'name2': 'value2', 'name3':'value3'}},
{'item2': {'name1': 'value1', 'name2': 'value2', 'name3':'value3'}},
{'item3': {'name1': 'value1', 'name2': 'value2', 'name3':'value3'}}]

I've looked into using a reducer, but it doesn't seem like the right fit for my scenario. Any help would be greatly appreciated!

typescript postgresql

Answer 1

Answer №1

Utilizing the reduce function is one approach, but allow me to provide you with the precise algorithmic solution as well.

To avoid the N+1 anti-pattern of performing one query per row, you can retrieve all rows in a single query by utilizing a

where itemId IN (<ids array>)

After gathering all the rows, it is crucial to create an index for efficient joining of rows with items (N*Log(N)). This can be achieved using a library such as lodash's indexBy, or with just 3 lines of code:

const detailsById = {};
res.rows.forEach(row => detailsById[row.itemId] = row); 
// where row.itemId is the linking element to list One items

For performing the join, you can utilize a reduce function in the following manner:

listOne.reduce((acc, itemId) => { acc[itemId] = detailsById[itemId]; return acc;} , {});

Answer 2

Utilizing the reduce function is one approach, but allow me to provide you with the precise algorithmic solution as well.

To avoid the N+1 anti-pattern of performing one query per row, you can retrieve all rows in a single query by utilizing a

where itemId IN (<ids array>)

After gathering all the rows, it is crucial to create an index for efficient joining of rows with items (N*Log(N)). This can be achieved using a library such as lodash's indexBy, or with just 3 lines of code:

const detailsById = {};
res.rows.forEach(row => detailsById[row.itemId] = row); 
// where row.itemId is the linking element to list One items

For performing the join, you can utilize a reduce function in the following manner:

listOne.reduce((acc, itemId) => { acc[itemId] = detailsById[itemId]; return acc;} , {});

Is it possible to create a nested object inside of an array?

Answer №1

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