add Replacing substrings recipe to Regular Expressions chapter

Author: phlipper

chapters/regular_expressions/replacing-substrings.md

@@ -0,0 +1,39 @@
+---
+layout: recipe
+title: Replacing substrings
+chapter: Regular Expressions
+---
+## Problem
+
+You need to replace a portion of a string with another value.
+
+## Solution
+
+Use the JavaScript `replace` method. `replace` matches with the given string, and returns the edited string.
+
+The first version takes 2 arguments: _pattern_ and _string replacement_
+
+{% highlight coffeescript %}
+"JavaScript is my favorite!".replace /Java/, "Coffee"
+# => 'CoffeeScript is my favorite!'
+
+"foo bar baz".replace /ba./, "foo"
+# => 'foo foo baz'
+
+"foo bar baz".replace /ba./g, "foo"
+# => 'foo foo foo'
+{% endhighlight %}
+
+The second version takes 2 arguments: _pattern_ and _callback function_
+
+{% highlight coffeescript %}
+"CoffeeScript is my favorite!".replace /(\w+)/g, (match) ->
+  match.toUpperCase()
+# => 'COFFEESCRIPT IS MY FAVORITE!'
+{% endhighlight %}
+
+The callback function is invoked for each match, and the match value is passed as the argument to the callback.
+
+## Discussion
+
+Regular Expressions are a powerful way to match and replace strings.

wanted-recipes.md

@@ -86,7 +86,6 @@ foo 1, 2, 3
 
 * Searching for substrings # "foo bar baz".match(/ba./) # => [ 'bar', index: 4, input: 'foo bar baz' ]
 * Searching for substrings # "foo bar baz".search(/ba./) # => 4
-* Replacing substrings # "foo bar baz".replace( /ba./, 'foo') # => "foo foo baz"
 
 ## Networking