diff --git a/binary_search.js b/binary_search.js
new file mode 100644
index 0000000..92d091f
--- /dev/null
+++ b/binary_search.js
@@ -0,0 +1,18 @@
+var search = function(nums, target) {
+  let lo = 0
+  let hi = nums.length
+  let mid
+
+  while(lo <= hi) {
+    mid = Math.floor((lo + hi)/2)
+
+    if (nums[mid] === target) {
+      return mid
+    } else if (nums[mid] > target) {
+      hi = mid - 1
+    } else {
+      lo = mid + 1
+    }
+  }
+  return -1
+};