Added insert module

index.js

@@ -68,6 +68,7 @@ const id = require('./src/id')
 const includes = require('./src/includes')
 const incr = require('./src/incr')
 const init = require('./src/init')
+const insert = require('./src/insert')
 const isArr = require('./src/is-arr')
 const isDate = require('./src/is-date')
 const isDef = require('./src/is-def')
@@ -272,6 +273,7 @@ module.exports = {
   includes,
   incr,
   init,
+  insert,
   isArr,
   isDate,
   isDef,

src/insert.js

@@ -0,0 +1,20 @@
+'use strict'
+const and = require('./and')
+const append = require('./append')
+const concat = require('./concat')
+const curry = require('./curry')
+const drop = require('./drop')
+const empty = require('./empty')
+const notArr = require('./not-arr')
+const notStr = require('./not-str')
+const reduce = require('./reduce')
+const take = require('./take')
+
+function insert(idx, x, xs) {
+  if (and(notArr(xs), notStr(xs)))
+    throw new TypeError('[insert] Last argument must be an array or a string')
+
+  return reduce(concat, empty(xs), [append(x, take(idx, xs)), drop(idx, xs)])
+}
+
+module.exports = curry(insert)