Add Spread Merging Objects Includes Nil Values as a JavaScript TIL

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

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+# 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`.