How to create an array of objects from multiple arrays

Question

Given the following arrays:

var ids = [1,2,3]; //Hundreds of elements here
var names = ["john","doe","foo"]; //Hundreds of elements here
var countries = ["AU","USA,"USA"]; //Hundreds of elements here

What's the best way performance-wise to generate an array of objects with a similar structure to this:

var items = [
 {id:1,name:"john",country:"AU"},
 {id:2,name:"doe",country:"USA"},
 ...
];

• kevin628: If there's one thing I can't say enough on SO, it's this: make it work first, then worry about performance if and only if performance becomes an issue. How would you solve this if you weren't concerned about performance?
• user663031: What kind of performance? Run-time? Memory? Lines of code? Writability/maintainability?
• user663031: I am wondering where you were getting stuck, since a simple solution is to loop from 0 to 2, then each time through the loop push an object containing the relevant values onto a results array. Once you've figured that out, you can move on to using map etc.

Answer 1

You should be able to simply map through all ids, keeping a reference to your index, and build your object based on that index.

var items = ids.map((id, index) => {
 return {
 id: id,
 name: names[index],
 country: countries[index]
 }
});

Answer 2

This is what I get when run the code:

[
 { country=AU, name=john, id=1.0 }, 
 { name=doe, country=USA, id=2.0 }, 
 { id=3.0, country=USA, name=foo }
]

Following is the code, same as @Zack Tanner

function arrs2Obj() {
 var ids = [1, 2, 3]; //Hundreds of elements here
 var names = ["john", "doe", "foo"]; //Hundreds of elements here
 var countries = ["AU", "USA", "USA"]; //Hundreds of elements here
 var items = ids.map((id, index) => {
 return {
 id: id,
 name: names[index],
 country: countries[index]
 }
 });
 Logger.log(items)
}

The problem is, this result is not sorted as the questioner asked. I mean it's not consistent - ids to be the first item, name second, country 3rd; this way it is more presentable.

• Shane: Just want to add that the ordering of fields in an object is not guaranteed. As per the JSON standard, "An object is an unordered collection of zero or more name/value pairs, where a name is a string and a value is a string, number, boolean, null, object, or array." - rfc-editor.org/rfc/rfc8259.html#section-1