JavaScript: Fundamentals - Revision history

40166222 at 14:34, 17 October 2018

2018-10-17T14:34:09Z

40166222 at 16:04, 2 October 2018

2018-10-02T16:04:39Z

← Older revision		Revision as of 16:04, 2 October 2018
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	This should be enough JavaScript to attempt the majority, if not all of the MongoDB questions on NoSQLZoo. <br/>		This should be enough JavaScript to attempt the majority, if not all of the MongoDB questions on NoSQLZoo. <br/>
			Some questions such as the harder MapReduce questions may be easier by reading up on [[JavaScript:_Computed_Properties \| Computed Properties]] beforehand. <br />
	Further tutorials can be found at the [https://developer.mozilla.org/en-US/docs/Web/JavaScript Mozilla Developer Network]		Further tutorials can be found at the [https://developer.mozilla.org/en-US/docs/Web/JavaScript Mozilla Developer Network]

40166222 at 10:25, 1 October 2018

2018-10-01T10:25:12Z

← Older revision		Revision as of 10:25, 1 October 2018
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	==Introduction to JavaScript==		==Introduction to JavaScript==
	JavaScript is a high level interpretted scripting language originally created to enable interactivity in web pages.<br/>		JavaScript is a high level interpretted scripting language originally created to enable interactivity in web pages.<br/>
	Today, JavaScript has many ~~additional applications~~, ~~and in particular~~ is ~~used by~~ MongoDB ~~to provide an~~ interactive shell environment.<br/>		Today, JavaScript has many other uses, one of which is powering the MongoDB interactive shell environment.<br/>
	As such, to be able to query MongoDB effectively it is necessary to have a good knowledge of both '''JavaScript (js)''' and '''JavaScript Object Notation (JSON)'''.		As such, to be able to query MongoDB effectively it is necessary to have a good knowledge of both '''JavaScript (js)''' and '''JavaScript Object Notation (JSON)'''.

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	===Variables and Types===		===Variables and Types===
	Variables are used to store values for later use. Each variable has a '''type''' which defines what kind of value can be stored, and what operations are allowed. Javascript has seven types in total:		Variables are used to store values for later use. Each variable has a '''type''' which defines what kind of value can be stored, and what operations are allowed involving that variable. Javascript has seven types in total:
	<br/><br/>		<br/><br/>
	<code>Number</code><br/>		<code>Number</code><br/>
	Any number, such a <code>1</code>, <code>-3.4</code>, or <code>2E9</code>.<br/>		Any number, such a <code>1</code>, <code>-3.4</code>, or <code>2E9</code>.<br/>
	In JavaScript all numbers are stored in floating point format.		In JavaScript all numbers are stored in [https://ieeexplore.ieee.org/document/4610935 IEEE floating-point format.]
	<div class="q nonum" data-lang="mongo">		<div class="q nonum" data-lang="mongo">
	<pre class="def"><nowiki>		<pre class="def"><nowiki>
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	<code>String</code><br/>		<code>String</code><br/>
	A string is a sequence of characters surrounded by quotation marks. e.g. <code>"Bob"</code>, <code>"Alice"</code><br/>		A string is a sequence of characters surrounded by quotation marks. e.g. <code>"Bob"</code>, <code>"Alice"</code><br/>
	There are several methods availible to making working with strings easier that can be found [https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String ~~Here~~].		There are several methods availible to making working with strings easier that can be found [https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String here].
	<div class="q nonum" data-lang="mongo">		<div class="q nonum" data-lang="mongo">
	<pre class="def"><nowiki>		<pre class="def"><nowiki>
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	</div>		</div>
	===Functions===		===Functions===
	~~Functions~~ are groups of statements that can be called by name to perform a certain task.~~<br/><br/>~~		In JavaScript, functions are groups of statements that can be called by name to perform a certain task.
	They can be either named, e.g. <code>function exampleFunction()</code>, or '''anonymous''', e.g. <code>function ()</code>. Typically anonymous functions in MongoDB are used as arguments to another function, such as <code>mapReduce</code>.<br/>		They can be either named, e.g. <code>function exampleFunction()</code>, or '''anonymous''', e.g. <code>function ()</code>.<br/><br/>
	Functions can optionally take variables as '''parameters''', also known '''arguments''', e.g. <code>function (1, 2)</code> and have the ability to '''return''' values too.~~<br/>~~
	If a function does not explicitly return a value or lacks a return statement entirely then the behavior is the same as <code>return undefined</code><br/><br/>		Typically anonymous functions in MongoDB are used as arguments to another function, such as <code>mapReduce</code>.<br/><br/>

			Functions can optionally take variables as '''parameters''', also known '''arguments''', e.g. <code>function (1, 2)</code> and have the ability to '''return''' values too. If a function does not explicitly return a value or lacks a return statement entirely then the behavior is the same as <code>return undefined</code><br/><br/>
	To refer to a function as a variable simply use it's name, e.g. <code>myFunc</code>.<br/>		To refer to a function as a variable simply use it's name, e.g. <code>myFunc</code>.<br/>
	To run a function you must '''call''' it by including parenthesis after the name, e.g. <code>myFunc()</code>		To run a function you must '''call''' it by including parenthesis after the name, e.g. <code>myFunc()</code>
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	// More examples at https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array</nowiki></pre>		// More examples at https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array</nowiki></pre>
	</div>		</div>


	This should be enough JavaScript to attempt the majority, if not all of the MongoDB questions on NoSQLZoo. <br/>		This should be enough JavaScript to attempt the majority, if not all of the MongoDB questions on NoSQLZoo. <br/>
	Further tutorials can be found at the [https://developer.mozilla.org/en-US/docs/Web/JavaScript Mozilla Developer Network]		Further tutorials can be found at the [https://developer.mozilla.org/en-US/docs/Web/JavaScript Mozilla Developer Network]

40166222 at 15:47, 20 July 2018

2018-07-20T15:47:12Z

@@ Line 224: / Line 224: @@
 print(y);    // 1</nowiki></pre>
 </div>
 ===Functions===
 Functions are groups of statements that can be called by name to perform a certain task.<br/><br/>
@@ Line 261: / Line 260: @@
 });</nowiki></pre>
 </div>

40166222: /* Function */

2018-07-20T14:01:18Z

Function

← Older revision		Revision as of 14:01, 20 July 2018
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	</div>		</div>

	===~~Function~~===		===Functions===
	Functions are groups of statements that can be called by name to perform a certain task.<br/><br/>		Functions are groups of statements that can be called by name to perform a certain task.<br/><br/>
	They can be either named, e.g. <code>function exampleFunction()</code>, or '''anonymous''', e.g. <code>function ()</code>. Typically anonymous functions in MongoDB are used as arguments to another function, such as <code>mapReduce</code>.<br/>		They can be either named, e.g. <code>function exampleFunction()</code>, or '''anonymous''', e.g. <code>function ()</code>. Typically anonymous functions in MongoDB are used as arguments to another function, such as <code>mapReduce</code>.<br/>

40166222: /* Function */

2018-07-20T13:40:54Z

Function

← Older revision		Revision as of 13:40, 20 July 2018
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	<div class="q nonum" data-lang="mongo">		<div class="q nonum" data-lang="mongo">
	<pre class="def"><nowiki>		<pre class="def"><nowiki>

	/* This function outputs "Hello World!" to screen.		/* This function outputs "Hello World!" to screen.
	*/		*/

40166222: /* Function */

2018-07-20T13:40:38Z

Function

@@ Line 226: / Line 226: @@
 ===Function===
-Functions are groups of statements that can be called by name to perform a certain task.<br/>
+Functions are groups of statements that can be called by name to perform a certain task.<br/><br/>
 They can be either named, e.g. <code>function exampleFunction()</code>, or '''anonymous''', e.g. <code>function ()</code>. Typically anonymous functions in MongoDB are used as arguments to another function, such as <code>mapReduce</code>.<br/>
-Functions can optionally take variables as '''parameters''', also known '''arguments''', e.g. <code>function (1, 2)</code> and have the ability to '''return''' values too. If a function does not explicity return a value the behaviour is the same as <code>return undefined</code>
+Functions can optionally take variables as '''parameters''', also known '''arguments''', e.g. <code>function (1, 2)</code> and have the ability to '''return''' values too.<br/>

40166222: /* Function */

2018-07-20T12:06:22Z

Function

← Older revision		Revision as of 12:06, 20 July 2018
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	===Function===		===Function===
	Functions~~, also known as methods or proceedures,~~ are ~~sets~~ of statements that perform a certain task. They can be either named, e.g. <code>function exampleFunction()</code>, or '''anonymous''', e.g. <code>function ()</code>. Typically anonymous functions in MongoDB are used as arguments to another function, such as <code>mapReduce</code>.<br/>		Functions are groups of statements that can be called by name to perform a certain task.<br/>
			They can be either named, e.g. <code>function exampleFunction()</code>, or '''anonymous''', e.g. <code>function ()</code>. Typically anonymous functions in MongoDB are used as arguments to another function, such as <code>mapReduce</code>.<br/>
	Functions can optionally take variables as '''parameters''', also known '''arguments''', e.g. <code>function (1, 2)</code> and have the ability to '''return''' values too. If a function does not explicity return a value the behaviour is the same as <code>return undefined</code>		Functions can optionally take variables as '''parameters''', also known '''arguments''', e.g. <code>function (1, 2)</code> and have the ability to '''return''' values too. If a function does not explicity return a value the behaviour is the same as <code>return undefined</code>

40166222: /* Assignments, and scope */

2018-07-20T12:03:31Z

Assignments, and scope

← Older revision		Revision as of 12:03, 20 July 2018
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	===Assignments, and scope===		===Assignments, and scope===
	To define and assign variables either use the <code>var</code> or <code>let</code> keyword.<br/><br/>		To define and assign variables either use the <code>var</code> or <code>let</code> keyword.<br/><br/>
	If declared outside of a function (discussed below) variables are '''global''', i.e. they can can be accessed and edited from anywhere. If used inside a function, <code>var</code> will use the scope of the entire function, whereas <code>let</code> variables will only affect the block in which they are defined.<br/><br/> To see this in action use the example below, which has been adapted from a Mozilla Developer Network example:		If declared outside of a function (discussed below) variables are '''global''', i.e. they can can be accessed and edited from anywhere.<br/>
			If used inside a function, <code>var</code> will use the scope of the entire function, whereas <code>let</code> variables will only affect the block in which they are defined.<br/><br/> To see this in action use the example below, which has been adapted from a Mozilla Developer Network example:
	<div class="q nonum" data-lang="mongo">		<div class="q nonum" data-lang="mongo">
	<pre class="def"><nowiki>		<pre class="def"><nowiki>
	var x = 1;		var x = 1; // declare a global variable, x
	if (true) {		if (true) {
	var x = 2; // same variable!		var x = 2; // same global variable, x
	print(x); // 2		print(x); // 2
	}		}
	print(x); // 2		print(x); // 2

	let y = 1;		let y = 1; // declare a global variable, y
	if (true) {		if (true) {
	let y = 2; // different variable		let y = 2; // different local variable, y
	print(y); // 2		print(y); // 2
	}		}

40166222: /* Assignments, and scope */

2018-07-20T12:02:11Z

Assignments, and scope

← Older revision		Revision as of 12:02, 20 July 2018
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	===Assignments, and scope===		===Assignments, and scope===
	To define and assign variables either use the <code>var</code> or <code>let</code> keyword.<br/><br/>		To define and assign variables either use the <code>var</code> or <code>let</code> keyword.<br/><br/>
	If declared outside of a function (discussed below) variables are '''global''', i.e. they can can be accessed and edited anywhere ~~below their declaration~~. If used inside a function, <code>var</code> will use the scope of the entire function, whereas <code>let</code> variables will only affect the block in which they are defined.<br/><br/> To see this in action use the example below, which has been adapted from a Mozilla Developer Network example:		If declared outside of a function (discussed below) variables are '''global''', i.e. they can can be accessed and edited from anywhere. If used inside a function, <code>var</code> will use the scope of the entire function, whereas <code>let</code> variables will only affect the block in which they are defined.<br/><br/> To see this in action use the example below, which has been adapted from a Mozilla Developer Network example:
	<div class="q nonum" data-lang="mongo">		<div class="q nonum" data-lang="mongo">
	<pre class="def"><nowiki>		<pre class="def"><nowiki>
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	print(y); // 1</nowiki></pre>		print(y); // 1</nowiki></pre>
	</div>		</div>

	===Function===		===Function===
	Functions, also known as methods or proceedures, are sets of statements that perform a certain task. They can be either named, e.g. <code>function exampleFunction()</code>, or '''anonymous''', e.g. <code>function ()</code>. Typically anonymous functions in MongoDB are used as arguments to another function, such as <code>mapReduce</code>.<br/>		Functions, also known as methods or proceedures, are sets of statements that perform a certain task. They can be either named, e.g. <code>function exampleFunction()</code>, or '''anonymous''', e.g. <code>function ()</code>. Typically anonymous functions in MongoDB are used as arguments to another function, such as <code>mapReduce</code>.<br/>
	Functions can optionally take variables as '''parameters''', also known '''arguments''', e.g. <code>function (1, 2)</code> and have the ability to '''return''' values too. If a function does not explicity return a value the behaviour is the same as <code>return undefined</code>		Functions can optionally take variables as '''parameters''', also known '''arguments''', e.g. <code>function (1, 2)</code> and have the ability to '''return''' values too. If a function does not explicity return a value the behaviour is the same as <code>return undefined</code>