---
title: "Destructuring and named parameters"
url: "https://www.bekk.christmas/post/2018/11/destructuring-and-named-parameters"
authors: ["Jan Amundsen"]
published: "2018-12-11"
updated: "2024-11-07T13:05:28Z"
language: "en-US"
type: "article"
tags: ["JavaScript"]
---

# Destructuring and named parameters

Destructuring your structures

In the magic year of 2015 I started my career in Bekk and we were introduced to destructuring in Javascript through ES6. Before this we had to assign values from objects and arrays the hard way.

```
position = {
  latitude: 59.911491,
  longitude: 10.757933,
}
let longitude = position.longitude;
let latitude = position.latitude;
console.log(`lat: ${latitude}, long: ${longitude}`); // lat: 59.911491, long: 10.757933
```

This can be really cumbersome for larger structures. Destructuring allow us to assign these values in a simpler way:

```
position = {
  latitude: 59.911491,
  longitude: 10.757933,
}
let { latitude, longitude } = position;
console.log(`lat: ${latitude}, long: ${longitude}`); // lat: 59.911491, long: 10.757933
```

### Custom variable names

If we wanted to name our variables `lat` and `long` instead we could destructure like this:

```
position = {
  latitude: 59.911491,
  longitude: 10.757933,
}
let { longitude: long, latitude: lat } = position;
console.log(`lat: ${lat}, long: ${long}`); // lat: 59.911491, long: 10.757933
```

While not as straightforward, it provide powerful flexibility to our destructuring.

### Nested destructuring

Destructuring nested objects is just as simple really. The difference is that we have to account for the structure when we assign the variables.

```
let city = {
  name: 'Oslo, Norway',
  position: {
    latitude: 59.911491,
    longitude: 10.757933,
  }
}
let { name, position: { longitude, latitude } } = city;
console.log(`${name} - lat: ${latitude}, long: ${longitude}`); // Oslo, Norway - lat: 59.911491, long: 10.757933
```

### Default values

To save ourself a lot of lines checking for undefined values if the property we try to assign from does not exist, we can set default values when we destructure.

```
let city = {
  name: 'Oslo, Norway',
}
let { name, position: { longitude = 0.0, latitude = 0.0 } = {} } = city;
console.log(`${name} - lat: ${latitude}, long: ${longitude}`); // Oslo, Norway - lat: 0.0, long: 0.0
```

As you can see in this example, we have to provide a default value to `position` as well as `latitude` and `longitude` for the default values in a nested object to work.

## Named parameters

When programming Javascript I use destructuring a lot as named parameters in functions.

```
const doSomthing = ({ a, b, c }) => {
  console.log(a,b,c);
}
doSomthing({a: 'test', b: 1, c: true}); // test 1 true
```

This allow us to use all the destructuring functionality above on the parameters to a function. Does providing default values to function parameters sound appealing? You bet. A long with other obvious advantages such as ignoring parameter ordering when using the function.

```
const doSomthing = ({ a = 'info', b, c = false }) => {
  console.log(a,b,c);
}
logValues({ b: 1, c: true}); // info 1 true
```

## Relevant resources recommended by the author

- [MDN docs - Destructuring assignment](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Destructuring_assignment)

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