Add Spread Merging Objects Includes Nil Values as a JavaScript TIL

README.md

@@ -10,7 +10,7 @@ pairing with smart people at Hashrocket.
 
 For a steady stream of TILs, [sign up for my newsletter](https://crafty-builder-6996.ck.page/e169c61186).
 
-_1227 TILs and counting..._
+_1228 TILs and counting..._
 
 ---
 
@@ -439,6 +439,7 @@ _1227 TILs and counting..._
 - [Sleep For A Bit In Async Code](javascript/sleep-for-a-bit-in-async-code.md)
 - [Sorting Arrays Of Objects With Lodash](javascript/sorting-arrays-of-objects-with-lodash.md)
 - [Splat Arguments To A Function](javascript/splat-arguments-to-a-function.md)
+- [Spread Merging Objects Includes Nil Values](javascript/spread-merging-objects-includes-nil-values.md)
 - [Spread The Rest With ES6](javascript/spread-the-rest-with-es6.md)
 - [Start Node Process In Specific Timezone](javascript/start-node-process-in-specific-timezone.md)
 - [String Interpolation With Template Literals](javascript/string-interpolation-with-template-literals.md)

javascript/spread-merging-objects-includes-nil-values.md

@@ -0,0 +1,27 @@
+# Spread Merging Objects Includes Nil Values
+
+A handy way to merge two objects together with ES6 JavaScript syntax is to use
+the [spread
+operator](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Spread_syntax).
+
+```javascript
+const combinedObj = { ...obj1, ...obj2 };
+```
+
+All the key-value pairs from each object are combined into a new object. For
+any overlapping keys, the last occurrence's value will take precedence.
+
+That bit about precedence is true for _nil_ values – `null` and `undefined` –
+as well.
+
+```javascript
+const obj1 = { taco: 'bell', hello: 'world', list: [1,2,3] }
+const obj2 = { burrito: 'house', hello: null, list: undefined }
+
+const combinedObj = { ...obj1, ...obj2 }
+//=> { taco: 'bell', hello: null, list: undefined, burrito: 'house' }
+```
+
+Notice that even though there are "actual" values for the `hello` and `list`
+keys in `obj1`, they are overridden by the `null` and `undefined` values in
+`obj2`.