refactor: improve level calculator (#1946)

Author: akmhmgc

src/calculateRank.js

@@ -63,29 +63,13 @@ function calculateRank({
 
   const normalizedScore = normalcdf(score, TOTAL_VALUES, ALL_OFFSETS) * 100;
 
-  let level = "";
-
-  if (normalizedScore < RANK_S_VALUE) {
-    level = "S+";
-  }
-  if (
-    normalizedScore >= RANK_S_VALUE &&
-    normalizedScore < RANK_DOUBLE_A_VALUE
-  ) {
-    level = "S";
-  }
-  if (
-    normalizedScore >= RANK_DOUBLE_A_VALUE &&
-    normalizedScore < RANK_A2_VALUE
-  ) {
-    level = "A++";
-  }
-  if (normalizedScore >= RANK_A2_VALUE && normalizedScore < RANK_A3_VALUE) {
-    level = "A+";
-  }
-  if (normalizedScore >= RANK_A3_VALUE && normalizedScore < RANK_B_VALUE) {
-    level = "B+";
-  }
+  const level = (() => {
+    if (normalizedScore < RANK_S_VALUE) return "S+";
+    if (normalizedScore >= RANK_S_VALUE && normalizedScore < RANK_DOUBLE_A_VALUE) return "S";
+    if (normalizedScore >= RANK_DOUBLE_A_VALUE && normalizedScore < RANK_A2_VALUE) return "A++";
+    if (normalizedScore >= RANK_A2_VALUE && normalizedScore < RANK_A3_VALUE) return "A+"
+    if (normalizedScore >= RANK_A3_VALUE && normalizedScore < RANK_B_VALUE)  return "B+"
+  })()
 
   return { level, score: normalizedScore };
 }