fix: update isUnique.js (careercup#68)

* Update isUnique.js

Using an object to store the occurrences, and check for duplication

* Update isUnique.js

Author: Rajasimhared

chapter01/1.1 - Is Unique/isUnique.js

@@ -23,6 +23,18 @@ const everyCharUnique = (str, indexOffset = 'a'.charCodeAt()) => {
     return true;
 };
 
+function everyCharUnique(str) {
+  let obj = {};
+  for (let i = 0; i < str.length; i++) {
+    if (obj[str[i]] && obj[str[i]] >= 1) {
+      return false;
+    } else {
+      obj[str[i]] = 1;
+    }
+  }
+  return true;
+}
+
 /* TESTS */
 console.log(everyCharUnique('abcd'), 'true');
 console.log(everyCharUnique('abccd'), 'false');