FIX: polyfills String.prototype.repeat for IE (#7994)

app/assets/javascripts/polyfills.js

@@ -316,4 +316,44 @@ if (!Array.from) {
   })();
 }
 
+// https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/repeat#Polyfill
+if (!String.prototype.repeat) {
+  String.prototype.repeat = function(count) {
+    "use strict";
+    if (this == null)
+      throw new TypeError("can't convert " + this + " to object");
+
+    var str = "" + this;
+    // To convert string to integer.
+    count = +count;
+    // Check NaN
+    if (count != count) count = 0;
+
+    if (count < 0) throw new RangeError("repeat count must be non-negative");
+
+    if (count == Infinity)
+      throw new RangeError("repeat count must be less than infinity");
+
+    count = Math.floor(count);
+    if (str.length == 0 || count == 0) return "";
+
+    // Ensuring count is a 31-bit integer allows us to heavily optimize the
+    // main part. But anyway, most current (August 2014) browsers can't handle
+    // strings 1 << 28 chars or longer, so:
+    if (str.length * count >= 1 << 28)
+      throw new RangeError(
+        "repeat count must not overflow maximum string size"
+      );
+
+    var maxCount = str.length * count;
+    count = Math.floor(Math.log(count) / Math.log(2));
+    while (count) {
+      str += str;
+      count--;
+    }
+    str += str.substring(0, maxCount - str.length);
+    return str;
+  };
+}
+
 /* eslint-enable */