Add Make The Browser Editable With Design Mode 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/).
 
-_846 TILs and counting..._
+_847 TILs and counting..._
 
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@@ -300,6 +300,7 @@ _846 TILs and counting..._
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 - [Link A JavaScript Package Locally](javascript/link-a-javascript-package-locally.md)
 - [List Top-Level NPM Dependencies](javascript/list-top-level-npm-dependencies.md)
+- [Make The Browser Editable With Design Mode](javascript/make-the-browser-editable-with-design-mode.md)
 - [Matching A Computed Property In Function Args](javascript/matching-a-computed-property-in-function-args.md)
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 - [Mock A Function With Return Values Using Jest](javascript/mock-a-function-with-return-values-using-jest.md)

javascript/make-the-browser-editable-with-design-mode.md

@@ -0,0 +1,15 @@
+# Make The Browser Editable With Design Mode
+
+Modern browsers support a Web API called _Design Mode_. When you turn on
+_Design Mode_, you are able to edit the text on the web page like you would do
+in Word or Dreamweaver. This is a great way to experiment with copy.
+
+By default it is `"off"`, but you can turn it on from your browser's devtools
+console.
+
+```
+> document.designMode = "on"
+"on"
+```
+
+[source](https://developer.mozilla.org/en-US/docs/Web/API/Document/designMode)