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# An Introduction to JavaScript
# JavaScript-e giriş

Let's see what's so special about JavaScript, what we can achieve with it, and which other technologies play well with it.
JavaScript-i beýle aýratyn edýän zat nämedigini göreliň, biz onuň bilen näme edip bileris we ol başga haysy tehnologiýalar bilen gowy işleýär.

## What is JavaScript?
## JavaScript näme?

*JavaScript* was initially created to "make web pages alive".
*JavaScript* ilkibaşda "web sahypalary interaktiw" etmek üçin döredilipdi.

The programs in this language are called *scripts*. They can be written right in a web page's HTML and run automatically as the page loads.
Bu dilde programmalara *skriptler (kod bölejikleri)* diýilýär. Skriptler HTML bilen birikdirilýär we web sahypa ýüklenen-den soň awtomatiki usulda işläp başlaýar.

Scripts are provided and executed as plain text. They don't need special preparation or compilation to run.
Skriptler arassa tekst görnüşinde berilýär we şol durşuna-da işledilýär. Olary işletmek üçin aýratyn taýýarlyk ýa-da kompliýasiýa gerek dal.

In this aspect, JavaScript is very different from another language called [Java](https://en.wikipedia.org/wiki/Java_(programming_language)).
Bu nukdaýnazardan, JavaScript [Java](https://en.wikipedia.org/wiki/Java_(programming_language)) dilinden düýbünden tapawutlanýar.

```smart header="Why is it called <u>Java</u>Script?"
When JavaScript was created, it initially had another name: "LiveScript". But Java was very popular at that time, so it was decided that positioning a new language as a "younger brother" of Java would help.
JavaScript ilkinji döredilende onuň ady: "LiveScript" boldy. Şol wagtlar Java dili has meşhurlyga eýe bolupdy, şeýlelikde JavaScript Java-nyň "jigisi" bolar diýen düşünje bilen onuň adyna meňzeş at dakmak kararyna geldiler.

But as it evolved, JavaScript became a fully independent language with its own specification called [ECMAScript](http://en.wikipedia.org/wiki/ECMAScript), and now it has no relation to Java at all.
Emma JavaScript kämilleşdigiçe, [ECMAScript](http://en.wikipedia.org/wiki/ECMAScript) diýilýän standartizasiýa guramasy bilen bilelikde düýbünden Java-dan garaşsyz dil boldy we häzir Java bilen adyndan başga hiç hili baglanyşygy ýok.
```

Today, JavaScript can execute not only in the browser, but also on the server, or actually on any device that has a special program called [the JavaScript engine](https://en.wikipedia.org/wiki/JavaScript_engine).
Häzirki günlerde, JavaScript diňe brauzer-de däl, eýsem serwer tarapda ýa-da bolmasa islendik enjamda [ JavaScript motory (the JavaScript engine)](https://en.wikipedia.org/wiki/JavaScript_engine) diýlip atlandyrylýan motoryň kömegi bilen işläp bilýar.

The browser has an embedded engine sometimes called a "JavaScript virtual machine".
Brauzer-iň içine "JavaScript virtual machine" diýen wirtual maşyn oturdylandyr.

Different engines have different "codenames". For example:
Her wirtual maşynyň özune mahsus "kod atlary" bardyr. Mysal üçin:

- [V8](https://en.wikipedia.org/wiki/V8_(JavaScript_engine)) -- in Chrome and Opera.
- [SpiderMonkey](https://en.wikipedia.org/wiki/SpiderMonkey) -- in Firefox.
- ...There are other codenames like "Chakra" for IE, "ChakraCore" for Microsoft Edge, "Nitro" and "SquirrelFish" for Safari, etc.
- [V8](https://en.wikipedia.org/wiki/V8_(JavaScript_engine)) -- Chrome we Opera üçin.
- [SpiderMonkey](https://en.wikipedia.org/wiki/SpiderMonkey) -- Firefox üçin.
- ...Başga-da IE(Internet Explorer) üçin "Chakra", Microsoft Edge üçin "ChakraCore", Safari üçin "Nitro" we "SquirrelFish" we ş.m.

The terms above are good to remember because they are used in developer articles on the internet. We'll use them too. For instance, if "a feature X is supported by V8", then it probably works in Chrome and Opera.
Ýokardaky atlary we adalgalary ýadyňyzda saklaň, sebabi olar internetdäki makalalarda ulanylýar. Olary biz hem ulanarys. Meselem, eger "X aýratynlyk V8 tarapyndan goldanylýar" diýilse, onda diýmek şol aýratynlyk Chrome we Opera brauzerlerinde işleýär diýmekdir.

```smart header="How do engines work?"

Engines are complicated. But the basics are easy.
Motorlar çylşyrymlydyr. Emma düýp esaslary aňsat.

1. The engine (embedded if it's a browser) reads ("parses") the script.
2. Then it converts ("compiles") the script to the machine language.
3. And then the machine code runs, pretty fast.
1. Motor (eger bir brauzer-e oturdylan bolsa (gömulen bolsa)) skriptleri okarýar ("parses").
2. Soňra ony maşyn diline öwürýär ("compiles").
3. we maşyn diline öwürlen kod çalt işleýär.

The engine applies optimizations at each step of the process. It even watches the compiled script as it runs, analyzes the data that flows through it, and further optimizes the machine code based on that knowledge.
Motor ýokardaky ädimleriň (prosesiň) dowamynda her ädimi optimizasiýa edýar. Hatda düzülen skriptiň işleýşine seredýär, içinden geçýän maglumatlary seljerýär we şol maglumatlaryň esasynda maşyn koduny hasam optimallaşdyrýar.
```

## What can in-browser JavaScript do?
## Brauzer-de JavaScript nämeler edip bilýär ?

Modern JavaScript is a "safe" programming language. It does not provide low-level access to memory or CPU, because it was initially created for browsers which do not require it.
Häzirki zaman JavaScript "howpsuz" programmirleme dildir. Ol pes-derejeli (low-level) operasiýalary ýerine ýetirmeýär, ýagny kompýuteriň ýadyna ýa-da prosessora (CPU) girip bilmeýär, sebabi ol ilkibaşda şu operasiýalara zerurlyk duýmaýan brauzer-ler üçin niýetlenipdi.

JavaScript's capabilities greatly depend on the environment it's running in. For instance, [Node.js](https://wikipedia.org/wiki/Node.js) supports functions that allow JavaScript to read/write arbitrary files, perform network requests, etc.
JavaScript-iň ukyplary onuň işleýän sferasyna baglydyr. Meselem, [Node.js](https://wikipedia.org/wiki/Node.js) faýllary okaýan/ýazýan, tor isleglerini ýerine ýetirýän, we ş.m. ýaly funksiýalary goldaýar.

In-browser JavaScript can do everything related to webpage manipulation, interaction with the user, and the webserver.
Brauzer-de JavaScript web sahypalary dolandyrmak, ulanyjy bilen interaksiýa (täsirleşmek) we brauzer-e degişli ähli zatlary edip biler.

For instance, in-browser JavaScript is able to:
Meselem, JavaScript brauzer-de şu aşakdakylary edip biler:

- Add new HTML to the page, change the existing content, modify styles.
- React to user actions, run on mouse clicks, pointer movements, key presses.
- Send requests over the network to remote servers, download and upload files (so-called [AJAX](https://en.wikipedia.org/wiki/Ajax_(programming)) and [COMET](https://en.wikipedia.org/wiki/Comet_(programming)) technologies).
- Get and set cookies, ask questions to the visitor, show messages.
- Remember the data on the client-side ("local storage").
- Sahypa täze HTML goşmak, bar bolan mazmuny üýtgetmek, stili (şekili) üýtgetmek.
- Ulanyjy hereketlerine jogap bermek, syçanjygyň hereketlerini ýerine ýetirmek, kursoryň herektlerini, klawişa basylanda emele gelýän wakalary ýerine ýetirmek.
- Tor-yň üsti bilen uzakdaky serwere maglumatlary ugratmak, faýllary indirmek(download) we ýüklemek (upload) ([AJAX](https://en.wikipedia.org/wiki/Ajax_(programming)) we [COMET](https://en.wikipedia.org/wiki/Comet_(programming)) diýip atlandyrylýan tehnologiýalar bilen).
- Cookie-leri almak we ýerleşdirmek, sahypany zyýarat edýänlere sorag bermek, habarlary (maglumatlary) görkezmek.
- Müşderi tarapynda (client-side) maglumatlary saklamak ("local storage").

## What CAN'T in-browser JavaScript do?
## JavaScript brauzer-de nameler edip bilmeýär ?

JavaScript's abilities in the browser are limited for the sake of the user's safety. The aim is to prevent an evil webpage from accessing private information or harming the user's data.
JavaScript-iň brauzerdäki ukyplary, ulanyjynyň howpsuzlygy üçin çäklidir. Esasy maksat, erbet web sahypasynyň şahsy maglumatlara girmeginiň ýa-da ulanyjynyň maglumatlaryna zyýan ýetirmeginiň öňüni almakdyr.

Examples of such restrictions include:
Şeýle çäklendirmelere şular girýär:

- JavaScript on a webpage may not read/write arbitrary files on the hard disk, copy them or execute programs. It has no direct access to OS functions.
- JavaScript web sahypada gaty disk-däki (hard disk) faýllary ýazyp/okap/pozup, olary göçürip alyp (kopýalap) ýa-da programmalary işledip bilmeýar. Onuň Operasion Sistema-nyň (OS) funksiýalaryna gös-göni girmäge rugsady ýokdur.

Modern browsers allow it to work with files, but the access is limited and only provided if the user does certain actions, like "dropping" a file into a browser window or selecting it via an `<input>` tag.
Häzirki zaman brauzerleri faýllar bilen işlemäge mümkinçilik berýär, emma giriş çäklidir we diňe ulanyjy faýly brauzeriň penjiresine "taşlamak" ýa-da `<input>` teg-i arkaly saýlamak ýaly käbir hereketleri eden ýagdaýynda üpjün edilýär.

There are ways to interact with camera/microphone and other devices, but they require a user's explicit permission. So a JavaScript-enabled page may not sneakily enable a web-camera, observe the surroundings and send the information to the [NSA](https://en.wikipedia.org/wiki/National_Security_Agency).
- Different tabs/windows generally do not know about each other. Sometimes they do, for example when one window uses JavaScript to open the other one. But even in this case, JavaScript from one page may not access the other if they come from different sites (from a different domain, protocol or port).
Kamera/mikrofon we beýleki gurluşlary ulanmagyň ýollary bar, emma munuň üçin ulanyjynyň aç-açan rugsady talap edilýär. Şonuň üçin JavaScript bilen işleýan web sahypa kamerany gizlinlikde işledip, daş-töweregi synlap we maglumatlary [NSA](https://en.wikipedia.org/wiki/National_Security_Agency)-a ugradyp bilmez.
- Dürli-dürli penjireleriň/tablaryň biri-biri bilen baglanyşygy ýokdur (biri beýlekisini tanamaýar). Käwagt şeýle edýärler, meselem bir sahypa beýelikini JavaScript ulanyp açjak bolanda. Emma şeýle ýagdaýda hem JavaScript-iň beýleki tab-a girmage rugsady ýokdur, eger-de başga saýtdan (domain-den, protocol-dan ýa-da port-dan) gelýän bolsa.

This is called the "Same Origin Policy". To work around that, *both pages* must agree for data exchange and contain a special JavaScript code that handles it. We'll cover that in the tutorial.

This limitation is, again, for the user's safety. A page from `http://anysite.com` which a user has opened must not be able to access another browser tab with the URL `http://gmail.com` and steal information from there.
- JavaScript can easily communicate over the net to the server where the current page came from. But its ability to receive data from other sites/domains is crippled. Though possible, it requires explicit agreement (expressed in HTTP headers) from the remote side. Once again, that's a safety limitation.
Muňa "Birmeňzeş gelip çykyş syýasaty"("Same Origin Policy") diýilýär. Munuň üstünde işlemek üçin * iki sahypa * maglumat alyşmak üçin biri-biri bilen ylalaşmaly we olary dolandyrýan ýörite JavaScript kody bolmaly. Munuň üstünde soňra durup geçeris.

Bu çäklendirme ulanyjynyň howpsuzlygy üçindir. Ulanyjynyň açan `http://anysite.com` sahypasy `http://gmail.com` URL bilen başga tab-a girip bilmez we ol ýerden maglumat ogurlap bilmez.
- JavaScript açan sahypaňyz-da aňsatlyk bilen serwer bilen bilelikde maglumat alyş-çalyş edip biler. Emma başga saýt/domain bilen maglumat alyş-çalyş edip bilmegi kän bir mümkin däl. Mümkin bolsa-da, oňa uzakdaky serwerden aç-açan ylalaşyk (HTTP header-de anlatmaly) zerurdyr. Ýene bir gezek gaýtalaýaryn, bu ulanyjynyň howpsuzlygy üçindir.

![](limitations.svg)

Such limits do not exist if JavaScript is used outside of the browser, for example on a server. Modern browsers also allow plugin/extensions which may ask for extended permissions.
Eger-de JavaScript brauzer-iň daşynda (meselem serwerde) ulanylsa, şeýle çäklendirmeler ýokdur. Häzirki zaman brauzerler giňeldilýän rugsatlary sorap bilýän plugin we extension-lere hem rugsat berýär.

## What makes JavaScript unique?
## JavaScript-i näme zat özboluşly edýär?

There are at least *three* great things about JavaScript:
JavaScript-i özboluşly edýän iň azyndan *üç* sany zady aýtmak bolar:

```compare
+ Full integration with HTML/CSS.
+ Simple things are done simply.
+ Support by all major browsers and enabled by default.
+ HTML/CSS bilen bilelikde dolulygyna işläp bilmegi.
+ Ýonekeý zatlary ýonekeýje edip bilmegi.
+ Tanymal ähli brauzer-ler tarapyndan goldanylýar we olarda deslapky (default) görnuşinde işleýändir.
```
JavaScript is the only browser technology that combines these three things.
JavaScript bu üç zady birleşdirýän ýeke-täk brauzer tehnologiýasydyr.

That's what makes JavaScript unique. That's why it's the most widespread tool for creating browser interfaces.
Ine JavaScript-i özboluşly edýän zat. Şonuň üçin brauzer interfeýslerini doretmek ulanylýänlygy üçin giňden ýaýrandyr.

That said, JavaScript also allows to create servers, mobile applications, etc.
Ýokarda belläp geçişimiz ýaly, JavaScript serwerleri döretmekde, mobil programmalary düzmekde, kompýuter programmalary we ş.m. ýerlerde ulanylýändyr.

## Languages "over" JavaScript
## JavaScript-iň "üstündäki" diller

The syntax of JavaScript does not suit everyone's needs. Different people want different features.
JavaScript-iň sintaksisi hemme kişiniň zerurlyklaryny doly laýyk gelenok. Her kim her hili aýratynlyklary isleýärler.

That's to be expected, because projects and requirements are different for everyone.
Ýagdaý şeýle, sebäbi her kişiniň proýektleri we zerurlyklary dürli-dürlidir.

So recently a plethora of new languages appeared, which are *transpiled* (converted) to JavaScript before they run in the browser.
Soňky döwürde brauzer-de işledilmezinden ozal JavaScript kodyna *transpiled* (öwrülen => converted) edilýän birnaçe dil emele geldi

Modern tools make the transpilation very fast and transparent, actually allowing developers to code in another language and auto-converting it "under the hood".
Häzirki zaman gurallar transplasiýany has tiz we aýdyn edip, programmistleriň başga dilde kod ýazmaklaryna mümkinçilik döretdiler.

Examples of such languages:
Şeýle dilleriň sanawy:

- [CoffeeScript](http://coffeescript.org/) is a "syntactic sugar" for JavaScript. It introduces shorter syntax, allowing us to write clearer and more precise code. Usually, Ruby devs like it.
- [TypeScript](http://www.typescriptlang.org/) is concentrated on adding "strict data typing" to simplify the development and support of complex systems. It is developed by Microsoft.
- [Flow](http://flow.org/) also adds data typing, but in a different way. Developed by Facebook.
- [Dart](https://www.dartlang.org/) is a standalone language that has its own engine that runs in non-browser environments (like mobile apps), but also can be transpiled to JavaScript. Developed by Google.
- [Brython](https://brython.info/) is a Python transpiler to JavaScript that allow to write application in pure Python without JavaScript.
- [CoffeeScript](http://coffeescript.org/) JavaScript üçin "syntactic sugar" (sintaktik şeker)-dir . Bize has gysga kod ýazmaga, arassa we takyk kod ýazmaga mümkinçilik berýär. Edil Ruby programmistleri ýaly.
- [TypeScript](http://www.typescriptlang.org/) çylşyrymly sistemalaryň ösüşini we goldawyny ýonekeýleşdirmek üçin "berk maglumat kysymlaryny" ýazmaga gönükdirilendir. TypeScript Microsoft tarapyndan döredilendir.
- [Flow](http://flow.org/) - munda hem "berk maglumat kysymlary"-ny goşup bilýärsiňiz, emma üýtgeşik usulda. Bu Facebook tarapyndan döredildi.
- [Dart](https://www.dartlang.org/) brazuer ýok ýerlerinde (mobil programmalar ýaly) işýleýän, ýöne JavaScript-e convert edip bolýan özbaşdak motory (engine) bolan garaşsyz bir dildir. Bu Google tarapyndan döredildi.
- [Brython](https://brython.info/) JavaScript-siz arassa Python kody bilen programma ýazmaga mümkinçilik berýän, JavaScript kodyna öwürýän Python transplýasiýasydyr.

There are more. Of course, even if we use one of transpiled languages, we should also know JavaScript to really understand what we're doing.
Ýene-de köp bar. Of course, even if we use one of transpiled languages, we should also know JavaScript to really understand what we're doing.

## Summary
## Gysgaça

- JavaScript was initially created as a browser-only language, but is now used in many other environments as well.
- Today, JavaScript has a unique position as the most widely-adopted browser language with full integration with HTML/CSS.
- There are many languages that get "transpiled" to JavaScript and provide certain features. It is recommended to take a look at them, at least briefly, after mastering JavaScript.
- JavaScript ilkibaşda diňe brauzer-de işleýän dil hökmünde döredilipdi, emma ol häzir başga birnäçe gurşawlarda işleýär.
- Häzirki wagtda JavaScript, HTML / CSS bilen doly integrasiýa bilen iň giňden kabul edilen brauzer dili hökmünde özboluşly orny eýeleýär.
- JavaScript-e "tranpirlenen" we käbir aýratynlyklary berýän köp dil bar. JavaScript-i özleşdirenden soň, iň bolmanda gysgaça olara göz aýlamak maslahat berilýär.