How to iterate over an array and constructing an object from the results of a PostgreSQL query

Question

Here's my problem:

var ps = ["P1", "P2"];
var hs = ["H1", "H2"];

var jOut = {};

hs.forEach(async (h) => {
    var t = `t_${h}`;
    var query = {
        text: `SELECT pName, pPrice FROM ${t} WHERE pName = ANY($1)`,
        values: [ps],
        rowMode: "array"
    };

    var qres = await client.query(query);
    jOut[t] = qres.rows;
});

console.log(jOut);

I want the output to look something like this:

{
    t_H1: [ [pName: "P1", pPrice: 0.5], [pName: "P2", pPrice: 1.2] ],
    t_H2: [ [pName: "P1", pPrice: 0.6], [pName: "P2", pPrice: 1.0] ]
}

But instead my output looks like this:

{}

Answer 1

forEach loop doesn't wait for promises until they are resolved, that's why

console.log(jOut);

is immediately executed before all/any of your promises are resolved.

Instead use for..of loop

for(const h of hs) {
 var t = `t_${h}`;
    var query = {
        text: `SELECT pName, pPrice FROM ${t} WHERE pName = ANY($1)`,
        values: [ps],
        rowMode: "array"
    };

    var qres = await client.query(query);
    jOut[t] = qres.rows;
}
console.log(jOut);