added finding all matches page

chapters/regular_expressions/finding-all-matches.md

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+---
+layout: recipe
+title: Finding All Matches
+chapter: Regular Expressions
+---
+## Problem
+
+You need to find all matches, not just the first.
+
+For example,
+
+{% highlight coffeescript %}
+/\d+/g.exec "I have 4 dogs, 7 cats, and 42 gold fish."
+# => ["4"]
+{% endhighlight %}
+
+## Solution
+
+{% highlight coffeescript %}
+RegExp::execAll = (haystack) ->
+    return [] unless @global
+    match[0] while match = @exec haystack
+
+text = "I have 4 dogs, 7 cats, and 42 gold fish."
+/d+/g.execAll text
+# => ["4", "7", "42"]
+{% endhighlight %}
+
+## Discussion
+
+The above throws away submatches, in order to simplify the result.  You can keep them with this variant.
+
+{% highlight coffeescript %}
+RegExp::execAll = (haystack) ->
+    return [] unless @global
+    match while match = @exec haystack
+
+/(\d+) (\w+)/g.execAll "I have 4 dogs, 7 cats, and 42 gold fish."
+# => [["4 dogs","4","dogs"],["7 cats","7","cats"],["42 gold","42","gold"]]
+{% endhighlight %}
+
+The first line of `execAll` prevents an infinite loop caused by non-global expressions.  This could be further 
+improved by creating a clone of the RegExp that is global, and use that.
+
+You must not save a reference to this expression (like `a = /xyx/g`) if you plan to call `execAll` more than once.  
+The same behavior be observed with the regular `exec` method.
+
+{% highlight coffeescript %}
+s = "I have 4 dogs, 7 cats, and 42 gold fish."
+myRegEx = /\d+/g
+myRegEx.exec s
+# => ["4"]
+myRegEx.execAll s
+# => ["7", "42"]
+myRegEx.exec s
+# => null
+{% endhighlight %}
+
+Instead use:
+
+{% highlight coffeescript %}
+/\d+/g.execAll s
+# => ["4", "7", "42"]
+/\d+/g.execAll s
+# => ["4", "7", "42"]
+{% endhighlight %}
+