assert: improve myers diff performance

fix: #57242

Author: puskin

lib/internal/assert/myers_diff.js

@@ -2,7 +2,6 @@
 
 const {
   ArrayPrototypePush,
-  ArrayPrototypeSlice,
   Int32Array,
   StringPrototypeEndsWith,
 } = primordials;
@@ -16,7 +15,7 @@ function areLinesEqual(actual, expected, checkCommaDisparity) {
     return true;
   }
   if (checkCommaDisparity) {
-    return `${actual},` === expected || actual === `${expected},`;
+    return (actual + ',') === expected || actual === (expected + ',');
   }
   return false;
 }
@@ -26,12 +25,10 @@ function myersDiff(actual, expected, checkCommaDisparity = false) {
   const expectedLength = expected.length;
   const max = actualLength + expectedLength;
   const v = new Int32Array(2 * max + 1);
-
   const trace = [];
 
   for (let diffLevel = 0; diffLevel <= max; diffLevel++) {
-    const newTrace = ArrayPrototypeSlice(v);
-    ArrayPrototypePush(trace, newTrace);
+    ArrayPrototypePush(trace, new Int32Array(v)); // Clone the current state of `v`
 
     for (let diagonalIndex = -diffLevel; diagonalIndex <= diffLevel; diagonalIndex += 2) {
       const offset = diagonalIndex + max;
@@ -89,22 +86,17 @@ function backtrack(trace, actual, expected, checkCommaDisparity) {
 
     while (x > prevX && y > prevY) {
       const actualItem = actual[x - 1];
-      const value =
-        !checkCommaDisparity || StringPrototypeEndsWith(actualItem, ',') ?
-          actualItem :
-          expected[y - 1];
+      const value = checkCommaDisparity && !StringPrototypeEndsWith(actualItem, ',') ? expected[y - 1] : actualItem;
       ArrayPrototypePush(result, { __proto__: null, type: 'nop', value });
       x--;
       y--;
     }
 
     if (diffLevel > 0) {
       if (x > prevX) {
-        ArrayPrototypePush(result, { __proto__: null, type: 'insert', value: actual[x - 1] });
-        x--;
+        ArrayPrototypePush(result, { __proto__: null, type: 'insert', value: actual[--x] });
       } else {
-        ArrayPrototypePush(result, { __proto__: null, type: 'delete', value: expected[y - 1] });
-        y--;
+        ArrayPrototypePush(result, { __proto__: null, type: 'delete', value: expected[--y] });
       }
     }
   }