fix(curriculum): replace window by self for js challenges

curriculum/challenges/english/02-javascript-algorithms-and-data-structures/es6/create-an-export-fallback-with-export-default.english.md

@@ -46,18 +46,18 @@ function subtract(x,y) {return x - y;}
 <div id='js-setup'>
 
 ```js
-window.exports = function(){};
+self.exports = function(){};
 ```
 
 </div>
 
-
 </section>
 
 ## Solution
 <section id='solution'>
 
 ```js
-// solution required
+export default function subtract(x,y) {return x - y;}
 ```
+
 </section>

curriculum/challenges/english/02-javascript-algorithms-and-data-structures/es6/import-a-default-export.english.md

@@ -45,22 +45,25 @@ subtract(7,4);
 <div id='js-setup'>
 
 ```js
-window.require = function(str) {
-if (str === 'math_functions') {
-return function(a, b) {
-return a - b;
-}}};
+self.require = function(str) {
+  if (str === 'math_functions') {
+    return function(a, b) {
+      return a - b;
+    }
+  }
+};
 ```
 
 </div>
 
-
 </section>
 
 ## Solution
 <section id='solution'>
 
 ```js
-// solution required
+import subtract from "math_functions";
+subtract(7,4);
 ```
+
 </section>

curriculum/challenges/english/02-javascript-algorithms-and-data-structures/es6/understand-the-differences-between-import-and-require.english.md

@@ -51,22 +51,25 @@ capitalizeString("hello!");
 <div id='js-setup'>
 
 ```js
-window.require = function (str) {
-if (str === 'string_functions') {
-return {
-capitalizeString: str => str.toUpperCase()
-}}};
+self.require = function (str) {
+  if (str === 'string_functions') {
+    return {
+      capitalizeString: str => str.toUpperCase()
+    }
+  }
+};
 ```
 
 </div>
 
-
 </section>
 
 ## Solution
 <section id='solution'>
 
 ```js
-// solution required
+import { capitalizeString } from 'string_functions';
+capitalizeString("hello!");
 ```
+
 </section>

curriculum/challenges/english/02-javascript-algorithms-and-data-structures/es6/use--to-import-everything-from-a-file.english.md

@@ -46,23 +46,25 @@ tests:
 <div id='js-setup'>
 
 ```js
-window.require = function(str) {
-if (str === 'capitalize_strings') {
-return {
-capitalize: str => str.toUpperCase(),
-lowercase: str => str.toLowerCase()
-}}};
+self.require = function(str) {
+  if (str === 'capitalize_strings') {
+    return {
+      capitalize: str => str.toUpperCase(),
+      lowercase: str => str.toLowerCase()
+    }
+  }
+};
 ```
 
 </div>
 
-
 </section>
 
 ## Solution
 <section id='solution'>
 
 ```js
-// solution required
+import * as capitalize_strings from "capitalize_strings";
 ```
+
 </section>

curriculum/challenges/english/02-javascript-algorithms-and-data-structures/es6/use-export-to-reuse-a-code-block.english.md

@@ -50,7 +50,7 @@ const bar = "foo";
 <div id='js-setup'>
 
 ```js
-window.exports = function(){};
+self.exports = function(){};
 ```
 
 </div>