From 3710647f46798dbc1a2c14ba63a95d3b0f8f6bf7 Mon Sep 17 00:00:00 2001
From: jbranchaud <jbranchaud@gmail.com>
Date: Mon, 10 Aug 2020 11:59:43 -0500
Subject: [PATCH] Add Interpolate A String Into A Regex as a javascript til

---
 README.md                                     |  3 +-
 .../interpolate-a-string-into-a-regex.md      | 31 +++++++++++++++++++
 2 files changed, 33 insertions(+), 1 deletion(-)
 create mode 100644 javascript/interpolate-a-string-into-a-regex.md

diff --git a/README.md b/README.md
index f6a745f..65c39e2 100644
--- a/README.md
+++ b/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).
 
-_944 TILs and counting..._
+_945 TILs and counting..._
 
 ---
 
@@ -333,6 +333,7 @@ _944 TILs and counting..._
 - [Immutable Remove With The Spread Operator](javascript/immutable-remove-with-the-spread-operator.md)
 - [Initialize A New JavaScript Project With Yarn](javascript/initialize-a-new-javascript-project-with-yarn.md)
 - [Install The Latest Version Of Node With Nvm](javascript/install-the-latest-version-of-node-with-nvm.md)
+- [Interpolate A String Into A Regex](javascript/interpolate-a-string-into-a-regex.md)
 - [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)
diff --git a/javascript/interpolate-a-string-into-a-regex.md b/javascript/interpolate-a-string-into-a-regex.md
new file mode 100644
index 0000000..9114f3a
--- /dev/null
+++ b/javascript/interpolate-a-string-into-a-regex.md
@@ -0,0 +1,31 @@
+# Interpolate A String Into A Regex
+
+You can build up strings with concatenation or the template literal syntax. If
+you're incorporating variables as part of this string building, that's called
+interpolation.
+
+But what if you need to interpolate variables into a regular expression
+(regex)?
+
+A regex literal looks like this:
+
+```javascript
+const myRegex = /^Some Customizable Text$/;
+```
+
+This works great for fixed strings, but won't cut it if you need to work
+_variable_ strings.
+
+What's needed to work with variables is the
+[`RegExp`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/RegExp)
+constructor:
+
+```javascript
+const customizableString = "Some Customizable Text";
+const myRegex = new RegExp(`^${customizableString}$`);
+```
+
+You can build up some string with string variables and regex syntax and `new
+RegExp()` will turn it into a regex.
+
+[source](https://makandracards.com/makandra/15879-javascript-how-to-generate-a-regular-expression-from-a-string)