add join

snippets/join.md

@@ -0,0 +1,18 @@
+### join
+
+
+
+```js
+const join = (arr,start = ',',end = start) => {
+      return arr.reduce((acc,val,i) => {
+       return  i == arr.length - 2 ? acc + val + end : i == arr.length - 1 ? acc + val : acc + val + start
+     },'')
+ }
+```
+
+```js
+join(); // ''
+join(['pen','pineapple','apple','pen'],',','&'); //"pen,pineapple,apple&pen"
+join(['pen','pineapple','apple','pen'],','); //"pen,pineapple,apple,pen"
+join(['pen','pineapple','apple','pen']); //"pen,pineapple,apple,pen"
+```