How to add variable into JSON path - node-postgres

Question

This is the query I am using:
app.get("/items/:data", async (req, res) => {
const { data } = req.params;
query = `
SELECT items.discount
FROM items
WHERE items.discount #? '$[*] ? (#.discount[*].shift == $1)'
`
try {
const obj = await pool.query(query, [data]);
res.json(obj.rows[0])
} catch(err) {
console.error(err.message);
}
});
I get this error:
error: bind message supplies 1 parameters, but prepared statement "" requires 0
I am using node-postgres package in node.js.
How can I solve this issue?

Answer 1

Use bracket notation instead of dot notation. So instead of obj.key use obj[key]

Answer 2

Updated
all them driver connectors come with their own method to do what you're looking for. node-postgres also have there own
Pool
import { Pool } from 'pg';
const pool = new Pool({
  host: 'localhost',
user: 'database-user',
max: 20,
idleTimeoutMillis: 30000,
connectionTimeoutMillis: 2000,
});
/**
* execs the given sql statement.
*
* #param {string} sql - query to run.
* #param {Array} params - an array with the parameter.
* #example
* runQuery("SELECT * FROM users WHERE id = $1", [1]).then(result=> console.log(result))
*/
export async function runQuery (sql, params) {
const connection = await pool.connect()
try {
await connection.query('BEGIN')
const queryText = 'INSERT INTO users(name) VALUES($1) RETURNING id'
const result = await connection.query(sql,params);
// check what result has
console.log(result);
return connection.query('COMMIT').then(result)
} catch (e) {
await connection.query('ROLLBACK')
throw e;
throw e
} finally {
connection.release()
}
}
Pool Config
config = {
// all valid client config options are also valid here
// in addition here are the pool specific configuration parameters:
// number of milliseconds to wait before timing out when connecting a new client
// by default this is 0 which means no timeout
connectionTimeoutMillis?: int,
// number of milliseconds a client must sit idle in the pool and not be checked out
// before it is disconnected from the backend and discarded
// default is 10000 (10 seconds) - set to 0 to disable auto-disconnection of idle clients
idleTimeoutMillis?: int,
// maximum number of clients the pool should contain
// by default this is set to 10.
max?: int,
}
conclution
so basically the structure of a query should be like or less this
const text = 'INSERT INTO users(name, email) VALUES($1, $2) RETURNING *'
const values = ['brianc', 'brian.m.carlson#gmail.com']
connection
.query(text, values)
.then(res => {
console.log(res.rows[0])
// { name: 'brianc', email: 'brian.m.carlson#gmail.com' }
})
.catch(e => console.error(e.stack))