Add Check If File Exists Before Reading It 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).
 
-_1275 TILs and counting..._
+_1276 TILs and counting..._
 
 ---
 
@@ -394,6 +394,7 @@ _1275 TILs and counting..._
 - [Character Codes from Keyboard Listeners](javascript/character-codes-from-keyboard-listeners.md)
 - [Check Classes On A DOM Element](javascript/check-classes-on-a-dom-element.md)
 - [Check If A Number Is Positive Or Negative](javascript/check-if-a-number-is-positive-or-negative.md)
+- [Check If File Exists Before Reading It](javascript/check-if-file-exists-before-reading-it.md)
 - [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)
 - [Compare The Equality Of Two Date Objects](javascript/compare-the-equality-of-two-date-objects.md)

javascript/check-if-file-exists-before-reading-it.md

@@ -0,0 +1,30 @@
+# Check If File Exists Before Reading It
+
+Let's say we are working on a script that tries to read in existing data from a
+JSON data file. It is possible that data file hasn't been created and populated
+yet. In order to account for that scenario, we need to check if the file
+exists. If we try to read from a non-existant file, an error will be thrown.
+
+To prevent the script from error'ing out, we can use
+[`fs.existsSync`](https://nodejs.org/api/fs.html#fsexistssyncpath) to check if
+the given file path is an existing file. If we learn that the file does exist,
+we can proceed with reading it. If not, we can skip the file read and react
+accordingly.
+
+```javascript
+import fs from 'fs'
+
+const nonExistantFile = 'non-existant.json'
+
+// set default in case file does not exists
+let json = {}
+
+if(fs.existsSync(nonExistantFile)) {
+  const fileData = fs.readFileSync(nonExistantFile)
+  json = JSON.parse(fileData.toString())
+}
+
+console.log('JSON: ', json)
+```
+
+[source](https://flaviocopes.com/how-to-check-if-file-exists-node/)