23 lines
713 B
Markdown
23 lines
713 B
Markdown
---
|
|
title: Assign default values for object properties
|
|
tags: object
|
|
cover: boats
|
|
firstSeen: 2018-01-19T13:51:05+02:00
|
|
lastUpdated: 2020-10-22T20:23:47+03:00
|
|
---
|
|
|
|
Assigns default values for all properties in an object that are `undefined`.
|
|
|
|
- Use `Object.assign()` to create a new empty object and copy the original one to maintain key order.
|
|
- Use `Array.prototype.reverse()` and the spread operator (`...`) to combine the default values from left to right.
|
|
- Finally, use `obj` again to overwrite properties that originally had a value.
|
|
|
|
```js
|
|
const defaults = (obj, ...defs) =>
|
|
Object.assign({}, obj, ...defs.reverse(), obj);
|
|
```
|
|
|
|
```js
|
|
defaults({ a: 1 }, { b: 2 }, { b: 6 }, { a: 3 }); // { a: 1, b: 2 }
|
|
```
|