Issue #3253735: Backbone manual tree-shake

core/misc/polyfills/array.includes.es6.js

+/**
+ * @file
+ * Provides a polyfill for Array.includes().
+ *
+ * This is needed for Internet Explorer 11 and Opera Mini.
+ *
+ * This has based on MDN Web Docs code samples. Code samples in the MDN Web Docs
+ * are licensed under CC0.
+ *
+ * @see https://web.archive.org/web/20161012020930/https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/includes
+ * @see https://developer.mozilla.org/en-US/docs/MDN/About#Code_samples_and_snippets
+ */
+if (!Array.prototype.includes) {
+  // eslint-disable-next-line no-extend-native
+  Array.prototype.includes = function (searchElement) {
+    if (this == null) {
+      throw new TypeError(
+        'Array.prototype.includes called on null or undefined',
+      );
+    }
+
+    const O = Object(this);
+    const len = parseInt(O.length, 10) || 0;
+    if (len === 0) {
+      return false;
+    }
+    // eslint-disable-next-line prefer-rest-params
+    const n = parseInt(arguments[1], 10) || 0;
+    let k;
+    if (n >= 0) {
+      k = n;
+    } else {
+      k = len + n;
+      if (k < 0) {
+        k = 0;
+      }
+    }
+    let currentElement;
+    while (k < len) {
+      currentElement = O[k];
+      if (
+        searchElement === currentElement ||
+        // eslint-disable-next-line no-self-compare
+        (searchElement !== searchElement && currentElement !== currentElement)
+      ) {
+        // NaN !== NaN
+        return true;
+      }
+      k += 1;
+    }
+    return false;
+  };
+}