Sync with upstream @ ea7738bb

1-js/02-first-steps/10-ifelse/article.md

@@ -68,7 +68,11 @@ if (podmínka) {
 
 ## Klauzule „else“
 
+<<<<<<< HEAD
 Příkaz `if` může obsahovat nepovinný blok „else“, který se vykoná, když podmínka je nepravdivá.
+=======
+The `if` statement may contain an optional `else` block. It executes when the condition is falsy.
+>>>>>>> ea7738bb7c3616bb51ff14ae3db2a2747d7888ff
 
 Příklad:
 ```js run

1-js/05-data-types/05-array-methods/article.md

@@ -255,7 +255,7 @@ alert( arr.includes(1) ); // true
 
 Please note that `indexOf` uses the strict equality `===` for comparison. So, if we look for `false`, it finds exactly `false` and not the zero.
 
-If we want to check if `item` exists in the array, and don't need the exact index, then `arr.includes` is preferred.
+If we want to check if `item` exists in the array, and don't need the index, then `arr.includes` is preferred.
 
 The method [arr.lastIndexOf](mdn:js/Array/lastIndexOf) is the same as `indexOf`, but looks for from right to left.
 
@@ -338,8 +338,6 @@ alert(users.findIndex(user => user.name == 'John')); // 0
 alert(users.findLastIndex(user => user.name == 'John')); // 3
 ```
 
-
-
 ### filter
 
 The `find` method looks for a single (first) element that makes the function return `true`.

5-network/10-long-polling/article.md

@@ -1,6 +1,6 @@
 # Long polling
 
-Long polling is the simplest way of having persistent connection with server, that doesn't use any specific protocol like WebSocket or Server Side Events.
+Long polling is the simplest way of having persistent connection with server, that doesn't use any specific protocol like WebSocket or Server Sent Events.
 
 Being very easy to implement, it's also good enough in a lot of cases.