A brief history on Javascript Photo by on Steve Halama Unsplash JavaScript was developed by He was asked to create a new language for Netscape Communications Corporations that would run on their browser and resembled Java in syntax so that their developers could learn that with minimum effort. It was launched by the name sometime in September 1995 and looking back all these years, some even call it a marketing stunt. Brendan Eich. JavaScript Need for standards in JavaScript: Microsoft looked to take over the browser market with and flushed out all the competition and implemented their own version of JavaScript. Internet Explorer The creators of JavaScript concluded the necessity of a standard in order to curb individual versions of JavaScript which would have become a developer’s nightmare in the absence of a proper standard which would later be called ECMA standard maintained by an organization called . ECMA International ECMAScript is born: In or came out and it was decided that . . From 2015 it was decided that a new ECMAScript standard would be rolled out each year and if a feature was not implemented by that time, it would simply not be included in that release. 1997 ECMAScript ES 1 JavaScript will be a language which implements ECMAScript ES 2 came out in 1998, ES 3 in 1999, ES 5 in 2009 and ES 6 or the officially called ES 2015 in 2015 ECMAScript release lifecycle: ECMA follows a process where there are 5 main processes: TC39 This where a proposal is not a formal proposal and suggestions or ideas are given by a TC39 member or a contributor to be brainstormed. Strawman or Stage 0: : This is where a proposal becomes formal and feature begins to be included in the release. A ‘Champion’ is responsible for a proposal. The TC39 committe actively participates in discussing the conflicts and suggests improvements to the feature. Proposal or Stage 1 If a proposal has come this far, it is likely to be a part of a standard later on which may not be this very release but the next one if it misses out on the current cycle. Two experimental examples are necessary to be implemented and its incremental changes are noted based on the feedback by the members. Draft or Stage 2: This is the stage where feedback from the outside world is taken into consideration. The designated reviewers sign off on the proposal. At this stage, changes to the proposal are to be made only in case critical issues arise. Candidate or Stage 3: Feature is going to be included in the next release and rigorous unit tests are done at this stage. Finished or Stage 4: You can view all the proposals and their state in this of ECMA. github repository ES 2017: This is the newest release in ECMA standard for JavaScript. Let us look at some of its new features. If you have any experience with the .NET world like me, you will find this extremely familiar. Although there may be some variations but it is much easier to understand if you already have some experience in C#. async and await: Do not get me wrong, it does not mean that people without C# experience will not get this, it is just that people with C# experience will feel a lot closer to home than others. Up to until ES 2016, this is how we made an asynchronous call using promises. Example in ES 2015 In case you are not familiar with arrow functions and ES 2015, as I have given the same implementation using ES 5 below, although you need to have some background with promises. You can skip the below image if you are comfortable with the one above. no need to worry Example with ES 5 functions. If I make the same implementation using the new keyword in ES 2017, it would look something like this. async and await using async and await in ES 2017 You can see the actual pen here This is how you can make an asynchronous call, without having to do download any external libraries by making an ‘ ’ request to the . xhr GET github api Just create an html file with a reference to your JavaScript file. This is needed because if you run your JavaScript file just using node, So go ahead and create an html file something like this you will end up violating the content security policy because then it will be treated as an attack as your JavaScript is not executing on the browser. just a simple html file with a reference to your JavaScript file. ‘ ’ is the file in my case. asynchrony.js asynchrony.js Simply walking through the code, here we have just made a function called ‘ ’ which just makes a GET request to the github api’s user resource to fetch my details and the response is returned inside of the ‘ ’ function as a json object which is logged to the console. asyncFn getMe Now, if we remove the keyword in , the ‘ will simply return a promise to which a resolve and a reject handler can be attached by using the ‘ ’ and ‘ ’ handlers respectively, so your ‘ ’ function becomes something like this await line 30 asyncFn’ then catch getMe without await So, using resolves your promises to the appropriate response object which can be a proper response when resolved and an erroneous response when rejected by the ‘ ’. await asyncFn Things to note: a) You cannot use an inside of a function unless that function is marked with keyword. await async b) If you are running with the visual studio code launcher, you need to install or other appropriate tool which will and add appropriate to the code so that your code could run with the launcher. Otherwise you would need to execute your ES 2017 code on a modern browser, most of the modern browsers can execute ES 2017 JavaScript code. babel transpile polyfills This is a fairly interesting concept. I would like to explain it with an analogy. When I was in college, I had in my first semester and the professor was an expert in but so much of an So he asked one of his students who was majoring in nuclear physics to cover for him. So in other words, the hideously prepared a test for us to take (pure evil) all this while waiting for to finish his job. 2. Web Workers: Physics atomic physics not expert in nuclear physics. main thread (the professor) assigned a worker thread (his student) to do a job for him while the main thread (professor) his student (the worker thread) The web worker executes as a different thread than the main thread which calls the worker and a different JavaScript file is executed for the worker thread and it does so independently, although, we can attach listeners to share data. Sharing of data happens by creation of a copied data for the worker so that it can work on it independently and then post its result back to the main thread. Before we begin to explore it with the code, let me tell you before hand that if you run this without hosting your app in the server, it won’t work because without the server, JavaScript is essentially a single threaded language and without the server’s dynamism, it won’t be able to start a different thread. Host your application using any web server, you can create a http server in node by using or by using the node module. Since learning how to create an http server in node is not our goal here, you can leave that task to node module. Just install it globally using and just start your server by running the command It will host your complete file system on In case you do not want to create an application, clone my git repository and once you have installed http-server node module just run the command Express http http-server npm install http-server -g http-server. http://localhost:8080 (the default port). https://gitlab.com/saurabhpati/es2017.git ‘ http-server ’. Now, create two javascript files one which will act as the and other which will act as the . I am going to keep it extremely minimalistic and as simple as possible. main worker thread web worker thread I have given my snapshot of my html file with reference to two scripts and how I ran the server and hosted that html on the server. Now all we have to do is to write the code for and myWorker.js mainWorker.js mainWorker.js: main worker code This code just creates a web worker, and the handler is a callback which executes when worker is done with its job. posts some data to the worker thread onmessage myWorker.js: do not get confused by I have not used any binding here, it is a understood by the server when the worker is being executed. I have attached the screenshot of the result below. ‘self’, ‘this’ dedicated worker global scope 3. Object.entries: introduced in gets the array of object keys, introduced in , gets the array of object values**.** ES 2017 has introduced an function which returns an array of arrays with containing both the keys and values, something like this. Object.keys , ES 5 , Object.values ECMA 2015 Object.entries using Object.entries result of Object.entries 4. Object.getOwnPropertyDescriptor/Object.getOwnPropertyDescriptors Now we can use the getOwnPropertyDescriptors method to get the object descriptor. code for getOwnPropertyDescriptors result You can also use Object.getOwnPropertyDescriptor(person, ‘age’) to get just the age descriptor alone. 5. padStart and padEnd: My name ‘Saurabh Pati’ is 12 characters, so if a start and an end padding is required we can do this now easily with ES 2017 as the start padding is done by characters in the code below, until a total length of 16 characters has been achieved. The padEnd function works similarly and keeps appending in the end of the string until a total length of 16 has been achieved. In case you use padding with 12 characters which is the same length as my name, . I have given the snapshots of the usages and result of these methods. #* ‘%$’ no padding is applied use of padEnd and padStart result of padStart and padEnd If you have reached this far, I would like to thank you for reading and in case you have any suggestions, kindly post them and I would make sure to work on each and every suggestion provided in order to improve myself and my content in future.

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