Merge 295fe153ad into 74514b462d

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below the description to indicate that this method of accessing an indefinite number of function arguments has been superseded by the use of the spread operator via rest parameters for ES6+ compatibility.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).
 
-_1505 TILs and counting..._
+_1506 TILs and counting..._
 
 ---
 
@@ -942,6 +942,7 @@ _1505 TILs and counting..._
 - [Demodulize A Class Name](rails/demodulize-a-class-name.md)
 - [Different Ways To Add A Foreign Key Reference](rails/different-ways-to-add-a-foreign-key-reference.md)
 - [Disambiguate Where In A Joined Relation](rails/disambiguate-where-in-a-joined-relation.md)
+- [Empty find_by Returns First Record](rails/empty-find-by-returns-first-record.md)
 - [Ensure A Rake Task Cannot Write Data](rails/ensure-a-rake-task-cannot-write-data.md)
 - [Ensure Migrations Use The Latest Schema](rails/ensure-migrations-use-the-latest-schema.md)
 - [Ensure Record Saved With after_commit Callback](rails/ensure-record-saved-with-after-commit-callback.md)

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);

rails/empty-find-by-returns-first-record.md

@@ -0,0 +1,49 @@
+# Empty find_by Returns First Record
+
+During a RubyConf 2024 talk, a speaker mentioned that if you pass `nil` to
+[ActiveRecord's `#find_by`
+method](https://api.rubyonrails.org/classes/ActiveRecord/FinderMethods.html#method-i-find_by),
+it will return the first record from the database. This is a bit unintuitive,
+so lets look at an example and then I'll show you why.
+
+```ruby
+> Book.first
+#=> #<Book:0x00000001142e4c48 id: 13, title: "The Secret History", ... >
+
+> Book.find_by(nil)
+#=> #<Book:0x00000001142ca3c0 id: 13, title: "The Secret History", ... >
+```
+
+So, that is the same object in both cases, but why?
+
+Our first hint is in the SQL that gets constructed when making that method
+call.
+
+```ruby
+Book Load (2.5ms)  SELECT "books".* FROM "books" LIMIT $1  [["LIMIT", 1]]
+```
+
+It's grabbing all books and limiting to _one_ result.
+
+Lets look at the underlying implementation of the `#find_by` method.
+
+```ruby
+# File activerecord/lib/active_record/relation/finder_methods.rb, line 111
+def find_by(arg, *args)
+  where(arg, *args).take
+end
+```
+
+Sure enough, the implementation is a `#where` followed by a `#take`. Since the
+`#where` is receiving `nil` as its `arg`, there are no conditions _filtering_
+the query. And the `#take` corresponds to the `limit 1`.
+
+Knowing that, we can understand that we will also get the first record from the
+database if we call `#find_by` with `{}`. Again, no conditions to filter on, so
+give me all books limited to one.
+
+One small caveat: notice how there is no `order by` clause in the above SQL
+output. This differs from `Books.first` which implicitly does an order on the
+`id` column. Though these method are likely to return the same result, the
+ordering of `#find_by` is not guaranteed to be the same without an `order by`
+clause.