Issue with concurrent (iterated) invocations of a function that calls Promise.all() - node.js

Question

This example is a simplification, but hopefully demonstrates my problem. I suspect I am missing something obvious re: closure here.
The issue is that results being returned from my aggregation function below include the final set of personParams i.e. those resulting from the final iteration of the forEach , not the set of personParams that the function was called with.
let promiseArray = []; // top level array of promises
let globalParams = { date: "2018-05-20" };
let people = [
{name: "Tom",
location: "Philadelphia"},
{name: "Bob",
location: "Austin"},
{name: "John",
location: "Philadelphia"}
];
people.forEach( person => {
// Create indivdiualized parameter set
let personParams = globalParams;
personParams.name = person.name;
personParams.location = person.location;
// Push promise to array
promiseArray.push(assembleResults(personParams));
});
Promise.all(promiseArray).then( results => {
console.log("Final Output:", results);
})
// individual data aggregation function
function assembleResults(iterationParams) {
let promise1 = Promise.resolve({data: "Type A data about " + iterationParams.name});
let promise2 = Promise.resolve({data: "Type B data about " + iterationParams.name});
let promise3 = Promise.resolve({data: "Type C data about " + iterationParams.name});
return Promise.all([promise1, promise2, promise3, iterationParams])
}
Updated with executable Fiddle # JSFiddle https://jsfiddle.net/shaunhurley/9r5k6j0c/
My expectation is that each iteration of assembleResults() is going to return an array that looks like:
[{data: "Type A data about <person's name>"},
{data: "Type B data about <person's name>"},
{data: "Type C data about <person's name>"},
{date: "2018-05-20", name: "<person's name>", location: "<location>"}]
Where each array will have name set to "Tom", "Bob" & "John" respectively. The final output would be an array or arrays per below.
[{data: "Type A data about Tom"},
{data: "Type B data about Tom"},
{data: "Type C data about Tom"},
{date: "2018-05-20", name: "Tom", location: "Philadelphia"}]
[{data: "Type A data about Bob"},
{data: "Type B data about Bob"},
{data: "Type C data about Bob"},
{date: "2018-05-20", name: "Bob", location: "Austin"}]
[{data: "Type A data about John"},
{data: "Type B data about John"},
{data: "Type C data about John"},
{date: "2018-05-20", name: "John", location: "Philadelphia"}]
The actual result is that, while the correct data sets are being returned, the parameter set included in each array is showing the last/final parameter set generated i.e. name == "John" and location == "Philadelphia"
[{data: "Type A data about Tom"},
{data: "Type B data about Tom"},
{data: "Type C data about Tom"},
{date: "2018-05-20", name: "John", location: "Philadelphia"}]
[{data: "Type A data about Bob"},
{data: "Type B data about Bob"},
{data: "Type C data about Bob"},
{date: "2018-05-20", name: "John", location: "Philadelphia"}]
[{data: "Type A data about John"},
{data: "Type B data about John"},
{data: "Type C data about John"},
{date: "2018-05-20", name: "John", location: "Philadelphia"}]
Any thoughts would be greatly appreciated...
Thanks!
Shaun

Answer 1

people.forEach(person => {
let personParams = globalParams;
personParams.name = person.name;
promiseArray.push(assembleResults(personParams));
});
In the above code block you called person.name where I can see each person is a String. So you are getting undefined instead of the person's name. I think it should be personParams.name = person.
And getResultsA getResultsB and getResultsC of assembleResults() function should not return any data unless you have some person called undefined.
I guess it's a dummy code you have posted. Posting the real code would have helped me answering more precisely.
Modification
Bellow code would do your job:
people.forEach((person) => {
// Create indivdiualized parameter set
const personParams = {
date: globalParams.date,
name: person.name,
location: person.location
}
// Push promise to array
promiseArray.push(assembleResults(personParams));
});
Explaining how did it work would take too long and I guess you already know why did it behave like that. Please google 'JavaScript object creation'.