Add Matching A Computed Property In Function Args as a javascript til

README.md

@@ -10,7 +10,7 @@ smart people at [Hashrocket](http://hashrocket.com/).
 For a steady stream of TILs from a variety of rocketeers, checkout
 [til.hashrocket.com](https://til.hashrocket.com/).
 
-_737 TILs and counting..._
+_738 TILs and counting..._
 
 ---
 
@@ -264,6 +264,7 @@ _737 TILs and counting..._
 - [ISO-8601 Formatted Dates Are Interpreted As UTC](javascript/iso-8601-formatted-dates-are-interpreted-as-utc.md)
 - [Link A JavaScript Package Locally](javascript/link-a-javascript-package-locally.md)
 - [List Top-Level NPM Dependencies](javascript/list-top-level-npm-dependencies.md)
+- [Matching A Computed Property In Function Args](javascript/matching-a-computed-property-in-function-args.md)
 - [Matching Multiple Values In A Switch Statement](javascript/matching-multiple-values-in-a-switch-statement.md)
 - [Mock A Function With Return Values Using Jest](javascript/mock-a-function-with-return-values-using-jest.md)
 - [New Dates Can Take Out Of Bounds Values](javascript/new-dates-can-take-out-of-bounds-values.md)

javascript/matching-a-computed-property-in-function-args.md

@@ -0,0 +1,28 @@
+# Matching A Computed Property In Function Args
+
+The [computed property name](http://es6-features.org/#ComputedPropertyNames)
+feature of ES6 allows you to reference a variable in object assignments and
+destructurings. This syntax is flexible enough that it can be used in the
+arguments portion of a function declaration. In fact, it can even be matched
+against another argument -- allowing the creation of some handy, yet terse
+functions.
+
+```javascript
+const get = (key, { [key]: foundValue }) => foundValue;
+```
+
+Notice that the first argument, `key`, will match against the computed
+property name in the second argument. The `foundValue` will correspond to
+whatever `key` maps to in the given object.
+
+This `get` function can then be used like so.
+
+```javascript
+const stuff = { a: 1, b: 2, c: 3 };
+
+console.log("Get a:", get("a", stuff)); // 1
+console.log("Get d:", get("d", stuff)); // undefined
+```
+
+h/t
+[@sharifsbeat](https://twitter.com/sharifsbeat/status/1084235020183748610)