Fix #1027: create IE11 Array polyfills `find` and `findIndex` in such a way that they are not iterable

HISTORY.md

@@ -7,6 +7,8 @@ https://github.com/josdejong/jsoneditor
 
 - Fixed broken link to the Ace editor website (https://ace.c9.io/).
   Thanks @p3x-robot.
+- Fix #1027: create IE11 Array polyfills `find` and `findIndex` in such a way 
+  that they are not iterable.
 
 
 ## 2020-05-24, version 9.0.0

src/js/polyfills.js

@@ -25,7 +25,8 @@ if (typeof Element !== 'undefined') {
 // simple polyfill for Array.findIndex
 if (!Array.prototype.findIndex) {
   // eslint-disable-next-line no-extend-native
-  Array.prototype.findIndex = function (predicate) {
+  Object.defineProperty(Array.prototype, 'findIndex', {
+    value: function (predicate) {
       for (let i = 0; i < this.length; i++) {
         const element = this[i]
         if (predicate.call(this, element, i, this)) {
@@ -33,16 +34,23 @@ if (!Array.prototype.findIndex) {
         }
       }
       return -1
-  }
+    },
+    configurable: true,
+    writable: true
+  })
 }
 
 // Polyfill for Array.find
 if (!Array.prototype.find) {
   // eslint-disable-next-line no-extend-native
-  Array.prototype.find = function (predicate) {
+  Object.defineProperty(Array.prototype, 'find', {
+    value: function (predicate) {
       const i = this.findIndex(predicate)
       return this[i]
-  }
+    },
+    configurable: true,
+    writable: true
+  })
 }
 
 // Polyfill for String.trim