Move internal modules to “internal” folder.

.internal/equalArrays.js

@@ -0,0 +1,84 @@
+import SetCache from './.internal/SetCache.js';
+import arraySome from './.internal/arraySome.js';
+import cacheHas from './.internal/cacheHas.js';
+
+/** Used to compose bitmasks for value comparisons. */
+const COMPARE_PARTIAL_FLAG = 1;
+const COMPARE_UNORDERED_FLAG = 2;
+
+/**
+ * A specialized version of `baseIsEqualDeep` for arrays with support for
+ * partial deep comparisons.
+ *
+ * @private
+ * @param {Array} array The array to compare.
+ * @param {Array} other The other array to compare.
+ * @param {number} bitmask The bitmask flags. See `baseIsEqual` for more details.
+ * @param {Function} customizer The function to customize comparisons.
+ * @param {Function} equalFunc The function to determine equivalents of values.
+ * @param {Object} stack Tracks traversed `array` and `other` objects.
+ * @returns {boolean} Returns `true` if the arrays are equivalent, else `false`.
+ */
+function equalArrays(array, other, bitmask, customizer, equalFunc, stack) {
+  const isPartial = bitmask & COMPARE_PARTIAL_FLAG;
+  const arrLength = array.length;
+  const othLength = other.length;
+
+  if (arrLength != othLength && !(isPartial && othLength > arrLength)) {
+    return false;
+  }
+  // Assume cyclic values are equal.
+  const stacked = stack.get(array);
+  if (stacked && stack.get(other)) {
+    return stacked == other;
+  }
+  let index = -1;
+  let result = true;
+  const seen = (bitmask & COMPARE_UNORDERED_FLAG) ? new SetCache : undefined;
+
+  stack.set(array, other);
+  stack.set(other, array);
+
+  // Ignore non-index properties.
+  while (++index < arrLength) {
+    let compared;
+    const arrValue = array[index];
+    const othValue = other[index];
+
+    if (customizer) {
+      compared = isPartial
+        ? customizer(othValue, arrValue, index, other, array, stack)
+        : customizer(arrValue, othValue, index, array, other, stack);
+    }
+    if (compared !== undefined) {
+      if (compared) {
+        continue;
+      }
+      result = false;
+      break;
+    }
+    // Recursively compare arrays (susceptible to call stack limits).
+    if (seen) {
+      if (!arraySome(other, (othValue, othIndex) => {
+            if (!cacheHas(seen, othIndex) &&
+                (arrValue === othValue || equalFunc(arrValue, othValue, bitmask, customizer, stack))) {
+              return seen.push(othIndex);
+            }
+          })) {
+        result = false;
+        break;
+      }
+    } else if (!(
+          arrValue === othValue ||
+            equalFunc(arrValue, othValue, bitmask, customizer, stack)
+        )) {
+      result = false;
+      break;
+    }
+  }
+  stack['delete'](array);
+  stack['delete'](other);
+  return result;
+}
+
+export default equalArrays;