-
Notifications
You must be signed in to change notification settings - Fork 0
/
index.html
370 lines (367 loc) · 23.8 KB
/
index.html
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
<!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">
<link rel="stylesheet" href="TechnicalDocumentationPage.css">
<title>Technical Documentation Page</title>
</head>
<body>
<nav id="navbar">
<header class="h-nav">JS Documentation</header>
<ul class="nav-ul">
<li class="nav-li"><a class="nav-link" href="#Introduction">Introduction</a></li>
<li class="nav-li"><a class="nav-link" href="#What_you_should_already_know">What you should already
know</a></li>
<li class="nav-li"><a class="nav-link" href="#JavaScript_and_Java">JavaScript and Java</a></li>
<li class="nav-li"><a class="nav-link" href="#Hello_world">Hello world</a></li>
<li class="nav-li"><a class="nav-link" href="#Variables">Variables</a></li>
<li class="nav-li"><a class="nav-link" href="#Declaring_variables">Declaring variables</a></li>
<li class="nav-li"><a class="nav-link" href="#Variable_scope">Variable scope</a></li>
<li class="nav-li"><a class="nav-link" href="#Global_variables">Global variables</a></li>
<li class="nav-li"><a class="nav-link" href="#Constants">Constants</a></li>
<li class="nav-li"><a class="nav-link" href="#Data_types">Data types</a></li>
<li class="nav-li"><a class="nav-link" href="#if...else_statement">if...else statement</a></li>
<li class="nav-li"><a class="nav-link" href="#while_statement">while statement</a></li>
<li class="nav-li"><a class="nav-link" href="#Function_declarations">Function declarations</a></li>
<li class="nav-li"><a class="nav-link" href="#Reference">Reference</a></li>
</ul>
</nav>
<main id="main-doc">
<!--section Introduction-->
<section class="main-section" id="Introduction">
<header class="primary-heading">Introduction</header>
<article>
<div class="paragraph">
<p class="para">JavaScript is a cross-platform, object-oriented scripting language. It is a small
and
lightweight language. Inside a host environment (for example, a web browser), JavaScript can be
connected to the objects of its environment to provide programmatic control over them.
</p>
<p class="para">JavaScript contains a standard library of objects, such as Array, Date, and Math,
and a
core set of
language elements such as operators, control structures, and statements. Core JavaScript can be
extended
for a variety of purposes by supplementing it with additional objects; for example:
</p>
<ul class="sec-ul">
<li class="sec-li">Client-side JavaScript extends the core language by supplying objects to
control
a browser and
its Document Object Model (DOM). For example, client-side extensions allow an application to
place elements on an HTML form and respond to user events such as mouse clicks, form input,
and
page navigation.
</li>
<li class="sec-li">Server-side JavaScript extends the core language by supplying objects
relevant to
running JavaScript on a server. For example, server-side extensions allow an application to
communicate with a database, provide continuity of information from one invocation to
another of
the application, or perform file manipulations on a server.
</li>
</ul>
</div>
</article>
</section>
<!--section What you should already know-->
<section class="main-section" id="What_you_should_already_know">
<header class="primary-heading">What you should already know</header>
<article>
<div class="paragraph">
<p class="para">This guide assumes you have the following basic background:</p>
<ul class="sec-ul">
<li class="sec-li">A general understanding of the Internet and the World Wide Web (WWW).</li>
<li class="sec-li">A general understanding of the Internet and the World Wide Web (WWW).</li>
<li class="sec-li">Some programming experience. If you are new to programming, try one of the
tutorials linked on the main page about JavaScript.</li>
</ul>
</div>
</article>
</section>
<!--section JavaScript and Java-->
<section class="main-section" id="JavaScript_and_Java">
<header class="primary-heading">JavaScript and Java</header>
<article>
<div class="paragraph">
<p class="para">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 class="para">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 class="para">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>
</div>
</section>
<!--section Hello world-->
<section class="main-section" id="Hello_world">
<header class="primary-heading">Hello world</header>
<article>
<div class="paragraph">
<p class="para">To get started with writing JavaScript, open the Scratchpad and write your first
"Hello
world" JavaScript code:
</p>
<code class="code">function greetMe(yourName) { alert("Hello " + yourName); }
greetMe("World");</code>
<p class="para">Select the code in the pad and hit Ctrl+R to watch it unfold in your browser!</p>
</article>
</div>
</section>
<!--section Variables-->
<section class="main-section" id="Variables">
<header class="primary-heading">Variables</header>
<article>
<div class="paragraph">
<p class="para">You use variables as symbolic names for values in your application. The names of
variables, called identifiers, conform to certain rules.
</p>
<p class="para">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 class="para">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>
</div>
</section>
<!--section Declaring variables-->
<section class="main-section" id="Declaring_variables">
<header class="primary-heading">Declaring variables</header>
<article>
<div class="paragraph">
<p class="para">You can declare a variable in three ways:</p>
<p class="para">With the keyword var. For example,</p>
<code class="code">var x = 42.</code>
<p class="para">This syntax can be used to declare both local and global variables.</p>
<p class="para">By simply assigning it a value. For example,</p>
<code class="code">x = 42.</code>
<p class="para">This always declares a global variable. It generates a strict JavaScript warning.
You shouldn't use this variant.</p>
<p class="para">With the keyword let. For example,</p>
<code class="code">let y = 13.</code>
<p class="para">This syntax can be used to declare a block scope local variable. See Variable scope
below.</p>
</article>
</div>
</section>
<!--section Variable scope-->
<section class="main-section" id="Variable_scope">
<header class="primary-heading">Variable scope</header>
<article>
<div class="paragraph">
<p class="para">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 class="para">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 class="code">if (true) { var x = 5; } console.log(x); // 5</code>
<p class="para">This behavior changes, when using the let declaration introduced in ECMAScript 2015.
</p>
<code class="code">if (true) { let y = 5; } console.log(y); // ReferenceError: y is not
defined</code>
</article>
</div>
</section>
<!--section Global variables-->
<section class="main-section" id="Global_variables">
<header class="primary-heading">Global variables</header>
<article>
<div class="paragraph">
<p class="para">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 class="para">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>
</div>
</section>
<!--section Constants-->
<section class="main-section" id="Constants">
<header class="primary-heading">Constants</header>
<article>
<div class="paragraph">
<p class="para">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 class="code">const PI = 3.14;</code>
<p class="para">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 class="para">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 class="para">You cannot declare a constant with the same name as a function or variable in the
same scope. For example:</p>
<code class="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 class="para">However, object attributes are not protected, so the following statement is executed
without problems.</p>
<code class="code">const MY_OBJECT = {"key": "value"}; MY_OBJECT.key = "otherValue";</code>
</article>
</div>
</section>
<!--section Data types-->
<section class="main-section" id="Data_types">
<header class="primary-heading">Data types</header>
<article>
<div class="paragraph">
<p class="para">The latest ECMAScript standard defines seven data types:</p>
<ul class="sec-ul">
<li class="sec-li">Six data types that are primitives:
<ul class="sec-ul">
<li class="sec-li">Boolean. true and false.</li>
<li class="sec-li">null. A special keyword denoting a null value. Because JavaScript is
case-sensitive, null is not the same as Null, NULL, or any other variant.</li>
<li class="sec-li">undefined. A top-level property whose value is undefined.</li>
<li class="sec-li">Number. 42 or 3.14159.</li>
<li class="sec-li">String. "Howdy"</li>
<li class="sec-li">Symbol (new in ECMAScript 2015). A data type whose instances are
unique
and immutable.</li>
</ul>
</li>
<li class="sec-li">and Object</li>
</ul>
<p class="para">Although these data types are a relatively small amount, they enable you to perform
useful functions with your applications. Objects and functions are the other fundamental
elements in the language. You can think of objects as named containers for values, and functions
as procedures that your application can perform.</p>
</article>
</div>
</section>
<!--section if...else statement-->
<section class="main-section" id="if...else_statement">
<header class="primary-heading">if...else statement</header>
<article>
<div class="paragraph">
<p class="para">Use the if statement to execute a statement if a logical condition is true. Use the
optional else clause to execute a statement if the condition is false. An if statement looks as
follows:</p>
<code class="code">if (condition) { statement_1; } else { statement_2; }</code>
<p class="para">condition can be any expression that evaluates to true or false. See Boolean for an
explanation of what evaluates to true and false. If condition evaluates to true, statement_1 is
executed; otherwise, statement_2 is executed. statement_1 and statement_2 can be any statement,
including further nested if statements.</p>
<p class="para">You may also compound the statements using else if to have multiple conditions
tested in sequence, as follows:</p>
<code class="code">if (condition_1) { statement_1; } else if (condition_2) { statement_2;
} else if (condition_n) { statement_n; } else { statement_last; }</code>
<p class="para">In the case of multiple conditions only the first logical condition which evaluates
to true will be executed. To execute multiple statements, group them within a block statement ({
... }) . In general, it's good practice to always use block statements, especially when nesting
if statements:</p>
<code class="code">if (condition) { statement_1_runs_if_condition_is_true;
statement_2_runs_if_condition_is_true; } else {
statement_3_runs_if_condition_is_false;
statement_4_runs_if_condition_is_false; }</code>
<p class="para">It is advisable to not use simple assignments in a conditional expression, because
the assignment can be confused with equality when glancing over the code. For example, do not
use the following code:</p>
<code class="code">if (x = y) { /* statements here */ }</code>
<p class="para">If you need to use an assignment in a conditional expression, a common practice is
to put additional parentheses around the assignment. For example:</p>
<code class="code">if ((x = y)) { /* statements here */ }</code>
</article>
</div>
</section>
<!--section while statement-->
<section class="main-section" id="while_statement">
<header class="primary-heading">while statement</header>
<article>
<div class="paragraph">
<p class="para">A while statement executes its statements as long as a specified condition evaluates
to true. A while statement looks as follows:</p>
<code class="code">while (condition) statement</code>
<p class="para">If the condition becomes false, statement within the loop stops executing and
control passes to the statement following the loop.</p>
<p class="para">The condition test occurs before statement in the loop is executed. If the condition
returns true, statement is executed and the condition is tested again. If the condition returns
false, execution stops and control is passed to the statement following while.</p>
<p class="para">To execute multiple statements, use a block statement ({ ... }) to group those
statements.</p>
<p class="para">Example:</p>
<p class="para">The following while loop iterates as long as n is less than three:</p>
<code class="code">var n = 0; var x = 0; while (n < 3) { n++; x += n; }</code>
<p class="para">With each iteration, the loop increments n and adds that value to x. Therefore, x
and n take on the following values:</p>
<ul class="sec-ul">
<li class="sec-li">After the first pass: n = 1 and x = 1</li>
<li class="sec-li">After the second pass: n = 2 and x = 3</li>
<li class="sec-li">After the third pass: n = 3 and x = 6</li>
</ul>
<p class="para">After completing the third pass, the condition n < 3 is no longer true, so the loop
terminates.</p>
</article>
</div>
</section>
<!--section Function declarations-->
<section class="main-section" id="Function_declarations">
<header class="primary-heading">Function declarations</header>
<article>
<div class="paragraph">
<p class="para">A function definition (also called a function declaration, or function statement)
consists of the function keyword, followed by:</p>
<ul class="sec-ul">
<li class="sec-li">The name of the function.</li>
<li class="sec-li">A list of arguments to the function, enclosed in parentheses and separated by
commas.</li>
<li class="sec-li">The JavaScript statements that define the function, enclosed in curly
brackets, { }.</li>
</ul>
<p class="para">For example, the following code defines a simple function named square:</p>
<code class="code">function square(number) { return number * number; }</code>
<p class="para">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 class="code">return number * number;</code>
<p class="para">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>
</div>
</section>
<!--section Reference-->
<section class="main-section" id="Reference">
<header class="primary-heading">Reference</header>
<article>
<div class="paragraph">
<ul class="sec-ul">
<li class="sec-li">All the documentation in this page is taken from <a
href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide">MDN</a></li>
</ul>
</article>
</div>
</section>
</main>
</body>
</html>