Add Pre And Post Hooks For Yarn Scripts as a JavaScript TIL

Author: jbranchaud

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).
 
-_1231 TILs and counting..._
+_1232 TILs and counting..._
 
 ---
 
@@ -432,6 +432,7 @@ _1231 TILs and counting..._
 - [Object Initialization With Shorthand Property Names](javascript/object-initialization-with-shorthand-property-names.md)
 - [Obtain Undefined Value With The Void Operator](javascript/obtain-undefined-value-with-the-void-operator.md)
 - [Parse A Date From A Timestamp](javascript/parse-a-date-from-a-timestamp.md)
+- [Pre And Post Hooks For Yarn Scripts](javascript/pre-and-post-hooks-for-yarn-scripts.md)
 - [Purge Null And Undefined Values From Object](javascript/purge-null-and-undefined-values-from-object.md)
 - [Random Cannot Be Seeded](javascript/random-cannot-be-seeded.md)
 - [Reach Into An Object For Nested Data With Get](javascript/reach-into-an-object-for-nested-data-with-get.md)

javascript/pre-and-post-hooks-for-yarn-scripts.md

@@ -0,0 +1,28 @@
+# Pre And Post Hooks For Yarn Scripts
+
+In [yarn](https://classic.yarnpkg.com/) v1, there is a special syntax for
+script names that allows you to define pre and post hooks.
+
+For instance, if you have a `build` script, you can define a `prebuild` and/or
+a `postbuild` script as well. Then, anytime you invoke `yarn build`, the
+`prebuild` script will be automatically run before `build` and the `postbuild`
+script be automatically run after `build`.
+
+This `pre{script}` and `post{script}` syntax works for any script.
+
+```json
+{
+  "scripts": {
+    "predeploy": "node pre-deploy-steps"
+    "deploy": "my-framework deploy",
+    "postdeploy": "node post-deploy-steps"
+  }
+}
+```
+
+This syntax may lead to unexpected script invocations. For instance, a
+`preserve` script will run ahead of a `serve` script even though those were
+probably intended to be unrelated scripts. This is, in part, why this syntax is
+no longer support in yarn v2.
+
+[source](https://classic.yarnpkg.com/lang/en/docs/cli/run/#toc-yarn-run-script)