From 8769155f5efb5df114730b9eb6e07926e3941941 Mon Sep 17 00:00:00 2001
From: is <isaac.ball@annkissam.com>
Date: Fri, 4 Oct 2019 21:59:58 -0400
Subject: [PATCH] update regexp

---
 regexp.md | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/regexp.md b/regexp.md
index 183a73188..79f6883fd 100644
--- a/regexp.md
+++ b/regexp.md
@@ -5,13 +5,12 @@ layout: 2017/sheet
 weight: -1
 authors:
   - github: rizqyhi
+  - github: izzergh
 updated: 2019-03-24
 description: |
   Basic cheatsheets for regular expression
 ---
 
-##
-
 {: .-three-column}
 
 ### Character classes
@@ -63,3 +62,12 @@ description: |
 | `a{3,}`  | Match 3 or more       |
 | `a{1,3}` | Match between 1 and 3 |
 
+### Lookahead & Lookbehind
+
+| Pattern      | Description                               |
+| ---          | ---                                       |
+| `a(?=b)`     | Match `a` in `baby` but not in `bay`      |
+| `a(?!b)`     | Match `a` in `Stan` but not in `Stab`     |
+| ---          | ---                                       |
+| `(?<=a)b`    | Match `b` in `crabs` but not in `cribs`   |
+| `(?<!a)b`    | Match `b` in `fib` but not in `fab`       |