Rename js snippets

snippets/js/s/default-values-for-object-properties.md

@@ -0,0 +1,23 @@
+---
+title: Assign default values for object properties
+type: snippet
+language: javascript
+tags: [object]
+cover: filter-coffee-pot
+dateModified: 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 }
+```