Understanding the inner workings of encapsulation in TypeScript

I'm diving into the world of encapsulation in Typescript and stumbled upon an example that has left me scratching my head. I am confused as to why I can access and modify the private members of a specific class directly.

class Encapsulate {
    str:string = "hello"
    private str2:string = "world"
}

var obj = new Encapsulate();
console.log(obj.str);     //accessible
obj.str2 = "something else";
console.log(obj.str2);   //compilation Error as str2 is private

OUTPUT: hello something else

Although I receive a compile time warning stating that there is a compilation error because str2 is private, I am still able to alter it and access it. This makes me question whether I truly understand what encapsulation is and how it operates in Typescript.

Answer №1

The issue lies in the fact that TypeScript simply transpiles to JavaScript, lacking any runtime environment of its own.

TypeScript provides warnings during compile time. It notifies you of:

Hey, Encapsulate str2 is private, and yet you're attempting to access it. That's not allowed.

However, once TypeScript transpiles and generates the JavaScript code, all TypeScript-specific annotations are gone from the code. JavaScript has no concept of private, enum, or interfaces. When your code compiles and runs in a browser or any other JavaScript runtime, you'll end up with an Encapsulate JavaScript object containing two fields, str1 and str2. These fields cannot be designated as private or public because JavaScript doesn't recognize those modifiers. Encapsulate will simply become a plain JavaScript object.

In essence, TypeScript assists in catching errors at compile time. However, after compilation, all TypeScript-related information is essentially 'forgotten'.

It may flag instances where you're trying to access str2 and might even prevent compilation if such an error is identified (depending on the tsconfig settings). Yet, the resulting compiled code will have no association with TypeScript.

Answer №2

It is not surprising that TypeScript behaves this way since it primarily focuses on static type checking. When the code is compiled into JavaScript, the operation being executed is deemed valid, resulting in no runtime errors.

Answer №3

In JavaScript, the concept of private and public members for a class does not exist (although this may change in the future). Currently, marking a property or function in a class as private is only validated at compile time (which is why a syntax error occurs).

Despite the syntax error generated by TypeScript, your code will still execute because TypeScript likely produced valid JavaScript code as output.

Similar questions

If you have not found the answer to your question or you are interested in this topic, then look at other similar questions below or use the search

Using jQuery for newly added data does not yield the desired results

<ul id="myul"> <li id="myli1"></li> <li id="myli2"></li> <li id="myli3"></li> . . . . <li id="myli15"></li> </ul> In my code, I have a list with unique IDs for each item. I also have implemented ...

Having trouble setting up discord.js on my device, getting an error message that says "Unable to install discord.js /

Trying to install Discord.JS by using the command npm install discord.js seems to be successful at first, but unfortunately it doesn't work as expected. Upon running the index.js file, an error message pops up indicating that the module discord.js is ...

What is the status of --async-stack-traces feature in node version 16 and above, and is there a replacement option available?

My query is similar to this one, but pertains to Node 16+. The response at the bottom of that thread mentions: For Node 14+ you can utilize the --async-stack-traces flag to enhance stack trace when dealing with asynchronous code. However, there are certain ...

An easy guide to accessing a file from an SD card using PhoneGap

I'm currently experimenting with PhoneGap's documentation tutorial by calling the window.requestFileSystem method only when I need to access a specific file, instead of inside the onDeviceReady function. However, I've encountered an issue wh ...

Solving required packages in Express server

I am encountering difficulties with resolving dependencies on my express server. Below is the structure of my project: Calculator --dist ----app -------calculator.js -------server.js --node_modules --src ----app --------calculator.js --------server.js -- ...

Utilizing AJAX requests to retrieve JSON data and populate Datatables

Trying to figure this out, but all I'm getting is [Object object]. Can anyone assist me with this issue? I've been following the Datatables documentation, but still can't seem to get it right. Any help would be greatly appreciated... thanks ...

I made numerous attempts to execute this task, but I'm facing difficulties with React State not updating when attempting to retrieve the account balance

Attempting to retrieve the account balance, I highlighted the h2 tag below for this purpose. However, when I console.log(this.state), I am only seeing the predefined values declared in the constructor and not the updated state: Link to image showing error ...

What is the best way to choose a single li element?

I am working on creating a reservation system using HTML, CSS, and JS. I want to customize the color of the border for each list item (li). However, I want only one li to be selected at a time. When I click on a different li, it should remove the selection ...

Is it considered valid in JavaScript or TypeScript to group values using (value1 || value2) for comparisons, and if it is, what is the reasoning behind

Does anyone know if using the || operator to group values while comparing a single variable is valid in the most recent versions of JavaScript or TypeScript? If not, what could be preventing this from becoming a valid syntactic sugar feature at some point? ...

Generate different choices in a DropDownList depending on the selection made in another DropDownList using JavaScript

I am currently working on implementing a search panel that will populate items based on the minimum and maximum price criteria. When looking at the front view of my page, it appears as follows: For instance, if I select a minimum price value of 100,000, t ...

Navigate through an overflowing element in react/next

I have a component with a fixed width and overflow-x-auto. I want to hide the scroll bar and replace it with arrow buttons for scrolling left and right. How can I add this functionality to my component? Here is the code for my component: <div className ...

YUI3 Searching with Selectors

I'm encountering an issue with selecting a single checkbox object in YUI3 based on its unique value attribute. In a table, there are multiple checkboxes with assigned unique keys to their value attributes. What should be the correct selector in YUI3 t ...

Ways to combine observables with just one observer receiving emitted values

Hello, I have a specific goal in mind with rxjs, but I am facing some challenges trying to achieve it within certain parameters. Here is what I aim to accomplish: first$ ---x| second$ ------x| subscribe -----------x| However, this is the c ...

Is it acceptable to reference all JS files in index.html in Angular?

Just dove into my first AngularJS project! Following a tutorial where they put everything in one controller, but now I want to separate controllers and services. I managed to split them into different JS files, but is it best practice to list all these f ...

Incorporating additional text following the creation of an image composite using HTML5

I am facing an issue with positioning two images on a canvas using HTML5. Despite changing the x and y properties, the images remain stuck at the top left corner (0, 0). This is different from how I can position text easily on the canvas. <canvas width ...

React-Webcam: What is the solution for the error "Object may be null" and how to resolve "Type null is not compatible with type string or undefined"?

I'm encountering an issue with const imageSrc = webcamRef.current.getScreenshot(); Error: Object is potentially 'null'; and src={imgSrc} <img src={imgSrc} /> Error: Type 'null' cannot be assigned to type 'string | und ...

Issue detected: The PNG file being used with jspdf is either incomplete or corrupt

I am trying to insert two images into my pdf when the "create-pdf" icon is clicked. The first image is a canvas that converts to an image successfully. var canvas = document.getElementsByClassName("jade-schematic-diagram"); img = canvas[0].toDataURL("imag ...

"Learn the trick to concealing a modal and unveiling a different one with the power of jquery

Whenever I try to open a modal, then click on a div within the modal in order to close it and open another one, I encounter an issue. The problem is that upon closing the first modal and attempting to display the second one, only the background of the seco ...

Struggling with a findIndex problem in React and JavaScript

Whenever I receive activeFilters values like this: const filter = [...activeFilters] The findIndex function always returns -1 even when the item I'm searching for exists. However, when I receive it like this, it works? const filter = activeFilters ...

Using an Angular dynamic ng-model name within an accordion

Looking for a way to make the ng-model name dynamic in this specific situation. Whenever a department is selected, the form needs to be updated accordingly. Currently, it works with ng-model="department.name", but this is causing some unexpected issues du ...