(hopefully) fix randomness

main.js

@@ -21,20 +21,38 @@ function with_move(board, move) {
 //     }
 //     return best_move;
 // }
+// classic: https://stackoverflow.com/questions/2450954/how-to-randomize-shuffle-a-javascript-array
+function shuffle(array) {
+    let currentIndex = array.length, randomIndex;
+    // While there remain elements to shuffle.
+    while (currentIndex != 0) {
+        // Pick a remaining element.
+        randomIndex = Math.floor(Math.random() * currentIndex);
+        currentIndex--;
+        // And swap it with the current element.
+        [array[currentIndex], array[randomIndex]] = [
+            array[randomIndex],
+            array[currentIndex],
+        ];
+    }
+    return array;
+}
 // could return early if zero but meh
 function min_move_by(board, score) {
     let best_score = Infinity;
     let best_move = "";
     let moves = board.moves();
+    shuffle(moves);
     // console.log(moves);
-    for (const i in moves) {
+    for (const move of moves) {
-        let move = moves[i];
         try {
             let new_board = with_move(board, move);
             let new_score = score(new_board);
             // console.log({ move, best_score, new_score, best_move });
-            if (new_score < best_score ||
+            if (new_score < best_score
-                (new_score == best_score && Math.random() > 0.5)) {
+            // array is already shuffled
+            // (new_score == best_score && Math.random() > 0.5)
+            ) {
                 console.log("New best (or equal): ", new_score, move);
                 best_score = new_score;
                 best_move = move;

main.ts

@@ -43,6 +43,26 @@ function with_move(board: Chess, move: string): Chess {
 
 //     return best_move;
 // }
+// classic: https://stackoverflow.com/questions/2450954/how-to-randomize-shuffle-a-javascript-array
+function shuffle(array) {
+    let currentIndex = array.length,
+        randomIndex;
+
+    // While there remain elements to shuffle.
+    while (currentIndex != 0) {
+        // Pick a remaining element.
+        randomIndex = Math.floor(Math.random() * currentIndex);
+        currentIndex--;
+
+        // And swap it with the current element.
+        [array[currentIndex], array[randomIndex]] = [
+            array[randomIndex],
+            array[currentIndex],
+        ];
+    }
+
+    return array;
+}
 
 // could return early if zero but meh
 function min_move_by(board: Chess, score: (_: Chess) => number): string {
@@ -50,17 +70,18 @@ function min_move_by(board: Chess, score: (_: Chess) => number): string {
     let best_move = "";
 
     let moves = board.moves();
+    shuffle(moves);
     // console.log(moves);
-    for (const i in moves) {
+    for (const move of moves) {
-        let move = moves[i];
         try {
             let new_board = with_move(board, move);
             let new_score = score(new_board);
             // console.log({ move, best_score, new_score, best_move });
 
             if (
-                new_score < best_score ||
+                new_score < best_score
-                (new_score == best_score && Math.random() > 0.5)
+                // array is already shuffled
+                // (new_score == best_score && Math.random() > 0.5)
             ) {
                 console.log("New best (or equal): ", new_score, move);
                 best_score = new_score;