Add defaults

snippets/defaults.md

@@ -0,0 +1,13 @@
+### defaults
+
+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.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 }
+```