Merge 295fe153ad into 43e6433fd6

Hello, I've added a small blockquote below the description to indicate that this method of accessing an indefinite number of function arguments has been superseded by the use of the spread operator via rest parameters for ES6+ compatibility.

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).
 
-_1539 TILs and counting..._
+_1540 TILs and counting..._
 
 ---
 
@@ -403,6 +403,7 @@ _1539 TILs and counting..._
 - [Access Go Docs Offline](go/access-go-docs-offline.md)
 - [Add A Method To A Struct](go/add-a-method-to-a-struct.md)
 - [Build For A Specific OS And Architecture](go/build-for-a-specific-os-and-architecture.md)
+- [Check If Cobra Flag Was Set](go/check-if-cobra-flag-was-set.md)
 - [Combine Two Slices](go/combine-two-slices.md)
 - [Do Something N Times](go/do-something-n-times.md)
 - [Find Executables Installed By Go](go/find-executables-installed-by-go.md)

go/check-if-cobra-flag-was-set.md

@@ -0,0 +1,41 @@
+# Check If Cobra Flag Was Set
+
+When using [Cobra](https://github.com/spf13/cobra) to define a CLI, we can
+specify a flag for a command like so:
+
+```go
+var Seed int64
+myCmd.PersistentFlags().Int64VarP(&Seed, "seed", "", -1, "set a seed")
+```
+
+This `--seed` flag has a _default_ of `-1`. If the flag isn't specified, then
+when we access that flag's value, we'll get `-1`.
+
+But how do we differentiate between the _default_ `-1` and someone passing `-1`
+to the `--seed` flag when running the program?
+
+In the command definition, we can look at the flags and see, by name, if
+specific ones were changed by user input rather than being the defaults.
+
+```go
+myCommand := &cobra.Command{
+	// coommand setup ...
+	Run: func(cmd *cobra.Command, args []string) {
+		if cmd.Flags().Changed("seed") {
+			seed, err := cmd.Flags().GetInt64("seed")
+			if err != nil {
+				fmt.Println("Seed flag is missing from `cmdFlags()`")
+				os.Exit(1)
+			}
+
+			fmt.Printf("Seed was set to %d\n", seed)
+		} else {
+			fmt.Println("Seed was not set")
+		}
+	}
+}
+```
+
+If we don't want to rely on the default and instead want to specify some other
+behavior when the flag is not manually set by the user, we can detect that
+scenario like this.

javascript/accessing-arguments-to-a-function.md

@@ -5,6 +5,8 @@ an array-like object with all of the arguments to the function. Even if not
 all of the arguments are referenced in the function signature, they can
 still be accessed via the `arguments` object.
 
+> For ES6+ compatibility, the `spread` operator used via [rest parameters](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Functions/rest_parameters) is preferred over the `arugments` object when accessing an abritrary number of function arguments.
+
 ```javascript
 function argTest(one) {
   console.log(one);