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<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8" />
<meta http-equiv="X-UA-Compatible" content="IE=edge" />
<meta name="viewport" content="width=device-width, initial-scale=1.0" />
<title>FCC Technical Documentation</title>
<link rel="stylesheet" href="styles.css" />
</head>
<body>
<nav id="navbar">
<header>JS Documentation</header>
<ul>
<li>
<a href="#Javascript_and_Java" class="nav-link">JavaScript and Java</a
>
</li>
<li><a href="#Hello_World" class="nav-link">Hello World</a></li>
<li><a href="#Variables" class="nav-link">Variables</a></li>
<li>
<a href="#Declaring_Variables" class="nav-link">Declaring Variables</a
>
</li>
<li><a href="#Variable_Scope" class="nav-link">Variable Scope</a></li>
<li>
<a href="#Global_Variables" class="nav-link">Global Variables</a>
</li>
<li><a href="#Constants" class="nav-link">Constants</a></li>
<li>
<a href="#Function_Declarations" class="nav-link">Function Declarations</a
>
</li>
</ul>
</nav>
<main id="main-doc">
<section class="main-section" id="Javascript_and_Java">
<header>JavaScript and Java</header>
<article>
<p>
JavaScript and Java are similar in some ways but fundamentally
different in some others. The JavaScript language resembles Java but
does not have Java's static typing and strong type checking.
JavaScript follows most Java expression syntax, naming conventions
and basic control-flow constructs which was the reason why it was
renamed from LiveScript to JavaScript.
</p>
<p>
In contrast to Java's compile-time system of classes built by
declarations, JavaScript supports a runtime system based on a small
number of data types representing numeric, Boolean, and string
values. JavaScript has a prototype-based object model instead of the
more common class-based object model. The prototype-based model
provides dynamic inheritance; that is, what is inherited can vary
for individual objects. JavaScript also supports functions without
any special declarative requirements. Functions can be properties of
objects, executing as loosely typed methods.
</p>
<p>
JavaScript is a very free-form language compared to Java. You do not
have to declare all variables, classes, and methods. You do not have
to be concerned with whether methods are public, private, or
protected, and you do not have to implement interfaces. Variables,
parameters, and function return types are not explicitly typed.
</p>
</article>
</section>
<section class="main-section" id="Hello_World">
<header>Hello World</header>
<article>
<p>
To get started with writing JavaScript, open the Scratchpad and
write your first "Hello world" JavaScript code:
</p>
<code
>function greetMe(yourName) { alert("Hello " + yourName); }
greetMe("World");</code
>
<p>
Select the code in the pad and hit Ctrl+R to watch it unfold in your
browser!
</p>
</article>
</section>
<section class="main-section" id="Variables">
<header>Variables</header>
<article>
<p>
You use variables as symbolic names for values in your application.
The names of variables, called identifiers, conform to certain
rules.
</p>
<p>
A JavaScript identifier must start with a letter, underscore (_), or
dollar sign ($); subsequent characters can also be digits (0-9).
Because JavaScript is case sensitive, letters include the characters
"A" through "Z" (uppercase) and the characters "a" through "z"
(lowercase).
</p>
<p>
You can use ISO 8859-1 or Unicode letters such as å and ü in
identifiers. You can also use the Unicode escape sequences as
characters in identifiers. Some examples of legal names are
Number_hits, temp99, and _name.
</p>
</article>
</section>
<section class="main-section" id="Declaring_Variables">
<header>Declaring Variables</header>
<article>
<p>You can declare a variable in three ways:</p>
<p>With the keyword var. For example,</p>
<code>var x = 42.</code>
<p>
This syntax can be used to declare both local and global variables.
</p>
<p>By simply assigning it a value. For example,</p>
<code>x = 42.</code>
<p>
This always declares a global variable. It generates a strict
JavaScript warning. You shouldn't use this variant.
</p>
<p>With the keyword let. For example,</p>
<code>let y = 13.</code>
<p>
This syntax can be used to declare a block scope local variable. See
Variable scope below.
</p>
</article>
</section>
<section class="main-section" id="Variable_Scope">
<header>Variable Scope</header>
<article>
<p>
When you declare a variable outside of any function, it is called a
global variable, because it is available to any other code in the
current document. When you declare a variable within a function, it
is called a local variable, because it is available only within that
function.
</p>
<p>
JavaScript before ECMAScript 2015 does not have block statement
scope; rather, a variable declared within a block is local to the
function (or global scope) that the block resides within. For
example the following code will log 5, because the scope of x is the
function (or global context) within which x is declared, not the
block, which in this case is an if statement.
</p>
<code>if (true) { var x = 5; } console.log(x); // 5</code>
<p>
This behavior changes, when using the let declaration introduced in
ECMAScript 2015.
</p>
<code
>if (true) { let y = 5; } console.log(y); // ReferenceError: y is
not defined</code
>
</article>
</section>
<section class="main-section" id="Global_Variables">
<header>Global Variables</header>
<article>
<p>
Global variables are in fact properties of the global object. In web
pages the global object is window, so you can set and access global
variables using the window.variable syntax.
</p>
<p>
Consequently, you can access global variables declared in one window
or frame from another window or frame by specifying the window or
frame name. For example, if a variable called phoneNumber is
declared in a document, you can refer to this variable from an
iframe as parent.phoneNumber.
</p>
</article>
</section>
<section class="main-section" id="Constants">
<header>Constants</header>
<article>
<p>
You can create a read-only, named constant with the const keyword.
The syntax of a constant identifier is the same as for a variable
identifier: it must start with a letter, underscore or dollar sign
and can contain alphabetic, numeric, or underscore characters.
</p>
<code>const PI = 3.14;</code>
<p>
A constant cannot change value through assignment or be re-declared
while the script is running. It has to be initialized to a value.
</p>
<p>
The scope rules for constants are the same as those for let block
scope variables. If the const keyword is omitted, the identifier is
assumed to represent a variable.
</p>
<p>
You cannot declare a constant with the same name as a function or
variable in the same scope. For example:
</p>
<code
>// THIS WILL CAUSE AN ERROR function f() {}; const f = 5; // THIS
WILL CAUSE AN ERROR ALSO function f() { const g = 5; var g;
//statements }</code
>
<p>
However, object attributes are not protected, so the following
statement is executed without problems.
</p>
<code
>const MY_OBJECT = {"key": "value"}; MY_OBJECT.key =
"otherValue";</code
>
</article>
</section>
<section class="main-section" id="Function_Declarations">
<header>Function Declarations</header>
<article>
<p>
A function definition (also called a function declaration, or
function statement) consists of the function keyword, followed by:
</p>
<ul>
<li>The name of the function.</li>
<li>
A list of arguments to the function, enclosed in parentheses and
separated by commas.
</li>
<li>
The JavaScript statements that define the function, enclosed in
curly brackets, { }.
</li>
<li>
Lorem ipsum dolor sit amet consectetur adipisicing elit. Deserunt,
ipsum.
</li>
<li>Lorem ipsum dolor sit amet consectetur adipisicing elit.</li>
</ul>
<p>
For example, the following code defines a simple function named
square:
</p>
<code>function square(number) { return number * number; }</code>
<p>
The function square takes one argument, called number. The function
consists of one statement that says to return the argument of the
function (that is, number) multiplied by itself. The return
statement specifies the value returned by the function.
</p>
<code>return number * number;</code>
<p>
Primitive parameters (such as a number) are passed to functions by
value; the value is passed to the function, but if the function
changes the value of the parameter, this change is not reflected
globally or in the calling function.
</p>
</article>
</section>
</main>
<script src="https://cdn.freecodecamp.org/testable-projects-fcc/v1/bundle.js"></script>
</body>
</html>