ELO snippet formatting + performance

Not assigning `arr.length` to a variable in a for loop means that the read is done on every iteration.

snippets/elo.md

@@ -15,17 +15,20 @@ const elo = ([...ratings], kFactor = 32, selfRating) => {
   const expectedScore = (self, opponent) => 1 / (1 + 10 ** ((opponent - self) / 400));
   const newRating = (rating, i) =>
     (selfRating || rating) + kFactor * (i - expectedScore(i ? a : b, i ? b : a));
+    
   if (ratings.length === 2) {
     return [newRating(a, 1), newRating(b, 0)];
-  } else {
-    for (let i = 0; i < ratings.length; i++) {
+  } 
+  
+  for (let i = 0, l = ratings.length; i < l; i++) {
     let j = i;
-      while (j < ratings.length - 1) {
+    
+    while (j < l - 1) {
       [ratings[i], ratings[j + 1]] = elo([ratings[i], ratings[j + 1]], kFactor);
       j++;
     }
   }
-  }
+  
   return ratings;
 };
 ```