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diff --git a/qutebrowser/javascript/quirks/array_at.user.js b/qutebrowser/javascript/quirks/array_at.user.js
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+// Based on: https://github.com/tc39/proposal-relative-indexing-method#polyfill
+
+/*
+Copyright (c) 2020 Tab Atkins Jr.
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.
+*/
+
+/* eslint-disable no-invalid-this */
+
+"use strict";
+
+(function() {
+    function at(idx) {
+        // ToInteger() abstract op
+        let n = Math.trunc(idx) || 0;
+        // Allow negative indexing from the end
+        if (n < 0) {
+            n += this.length;
+        }
+        // OOB access is guaranteed to return undefined
+        if (n < 0 || n >= this.length) {
+            return undefined;
+        }
+        // Otherwise, this is just normal property access
+        return this[n];
+    }
+
+    const TypedArray = Reflect.getPrototypeOf(Int8Array);
+    for (const type of [Array, String, TypedArray]) {
+        Object.defineProperty(
+            type.prototype,
+            "at",
+            {
+                "value": at,
+                "writable": true,
+                "enumerable": false,
+                "configurable": true,
+            }
+        );
+    }
+})();