Function main sync

1-js/02-first-steps/15-function-basics/1-if-else-required/solution.md

@@ -1 +1,3 @@
-No difference.
+No difference!
+
+In both cases, `return confirm('Did parents allow you?')` executes exactly when the `if` condition is falsy.

1-js/02-first-steps/15-function-basics/article.md

@@ -24,7 +24,7 @@ The `function` keyword goes first, then goes the *name of the function*, then a
 
 ```js
 function name(parameter1, parameter2, ... parameterN) {
-  ...body...
+ // body
 }
 ```
 
@@ -176,7 +176,7 @@ When a value is passed as a function parameter, it's also called an *argument*.
 
 In other words, to put these terms straight:
 
-- A parameter is the variable listed inside the parentheses in the function declaration (it's a declaration time term)
+- A parameter is the variable listed inside the parentheses in the function declaration (it's a declaration time term).
 - An argument is the value that is passed to the function when it is called (it's a call time term).
 
 We declare functions listing their parameters, then call them passing arguments.
@@ -206,7 +206,13 @@ function showMessage(from, *!*text = "no text given"*/!*) {
 showMessage("Ann"); // Ann: no text given
 ```
 
-Now if the `text` parameter is not passed, it will get the value `"no text given"`
+Now if the `text` parameter is not passed, it will get the value `"no text given"`.
+
+The default value also jumps in if the parameter exists, but strictly equals `undefined`, like this:
+
+```js
+showMessage("Ann", undefined); // Ann: no text given
+```
 
 Here `"no text given"` is a string, but it can be a more complex expression, which is only evaluated and assigned if the parameter is missing. So, this is also possible:
 
@@ -225,9 +231,41 @@ In the example above, `anotherFunction()` isn't called at all, if the `text` par
 On the other hand, it's independently called every time when `text` is missing.
 ```
 
+````smart header="Default parameters in old JavaScript code"
+Several years ago, JavaScript didn't support the syntax for default parameters. So people used other ways to specify them.
+
+Nowadays, we can come across them in old scripts.
+
+For example, an explicit check for `undefined`:
+
+```js
+function showMessage(from, text) {
+*!*
+  if (text === undefined) {
+    text = 'no text given';
+  }
+*/!*
+
+  alert( from + ": " + text );
+}
+```
+
+...Or using the `||` operator:
+
+```js
+function showMessage(from, text) {
+  // If the value of text is falsy, assign the default value
+  // this assumes that text == "" is the same as no text at all
+  text = text || 'no text given';
+  ...
+}
+```
+````
+
+
 ### Alternative default parameters
 
-Sometimes it makes sense to assign default values for parameters not in the function declaration, but at a later stage.
+Sometimes it makes sense to assign default values for parameters at a later stage after the function declaration.
 
 We can check if the parameter is passed during the function execution, by comparing it with `undefined`:
 
@@ -422,7 +460,7 @@ These examples assume common meanings of prefixes. You and your team are free to
 ```smart header="Ultrashort function names"
 Functions that are used *very often* sometimes have ultrashort names.
 
-For example, the [jQuery](http://jquery.com) framework defines a function with `$`. The [Lodash](http://lodash.com/) library has its core function named `_`.
+For example, the [jQuery](https://jquery.com/) framework defines a function with `$`. The [Lodash](https://lodash.com/) library has its core function named `_`.
 
 These are exceptions. Generally function names should be concise and descriptive.
 ```
@@ -490,7 +528,7 @@ function name(parameters, delimited, by, comma) {
 
 To make the code clean and easy to understand, it's recommended to use mainly local variables and parameters in the function, not outer variables.
 
-It is always easier to understand a function which gets parameters, works with them and returns a result than a function which gets no parameters, but modifies outer variables as a side-effect.
+It is always easier to understand a function which gets parameters, works with them and returns a result than a function which gets no parameters, but modifies outer variables as a side effect.
 
 Function naming: