Merge branch 'Ryan' into 'master'

add alert message for custom input

See merge request !31

src/components/Preview/Preview.tsx

-import { equals } from 'ramda';
+import { equals, isEmpty } from 'ramda';
 import { useState } from 'react';
 import { useSelectionSort, useBubbleSort, useInsertionSort, useCombSort, useShellSort, useCountingSort } from '../../hooks/algorithm';
 import { calculateColumnWidth, getRandomArray, getArray } from '../useFunctions/useFunctions';
@@ -76,7 +76,11 @@ function Preview({ useSort } : PreviewProps) {
   }
 
   const handleCreateCustomArray = () => {
-    setColumnsArray(getArray(max, 1, stringToArray(customArray)));
+    if(isEmpty(customArray.replace(/\D/g, ''))){
+      alert("input doesn't contain any numbers");
+    } else {
+      setColumnsArray(getArray(max, 1, stringToArray(customArray)));
+    }
   }
 
   console.log(highlight);