Add Conditionally Include Pairs In An Object as a javascript til

README.md

@@ -9,7 +9,7 @@ and pairing with smart people at Hashrocket.
 
 For a steady stream of TILs, [sign up for my newsletter](https://tinyletter.com/jbranchaud).
 
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@@ -287,6 +287,7 @@ _888 TILs and counting..._
 - [Check If Something Is An Array](javascript/check-if-something-is-an-array.md)
 - [Check The Password Confirmation With Yup](javascript/check-the-password-confirmation-with-yup.md)
 - [Computed Property Names In ES6](javascript/computed-property-names-in-es6.md)
+- [Conditionally Include Pairs In An Object](javascript/conditionally-include-pairs-in-an-object.md)
 - [Configure Jest To Run A Test Setup File](javascript/configure-jest-to-run-a-test-setup-file.md)
 - [Create A Cancelable Promise With PCancelable](javascript/create-a-cancelable-promise-with-pcancelable.md)
 - [Create An Array Containing 1 To N](javascript/create-an-array-containing-1-to-n.md)

javascript/conditionally-include-pairs-in-an-object.md

@@ -0,0 +1,35 @@
+# Conditionally Include Pairs In An Object
+
+You can add key-value pairs to an object using the ES6 spread operator:
+
+```javascript
+> { one: 1, ...{ hello: "world" } }
+{ one: 1, hello: "world" }
+```
+
+By combining the spread operator with some boolean logic, you can conditionally
+add key-value pairs to an object:
+
+```javascript
+> {
+    one: 1,
+    ...(isArriving && { hello: "world" }),
+  }
+```
+
+Depending on the value of `isArriving`:
+
+```javascript
+// isArriving === true
+{ one: 1, hello: "world" }
+```
+
+or
+
+```javascript
+// isArriving === false
+{ one: 1 }
+```
+
+This is useful for dynamically building up some configuration object or data
+payload.