A job interview is a situation that we all face in our career path. The interview is more important, especially for programming jobs compared to other jobs. The programmer must be able to show all his technical abilities and his motivation and enthusiasm for programming and cooperation with a company in a job interview.

1. Explain design patterns in JavaScript.

Design patterns in JavaScript are a set of repeatable methods and patterns used in programming to solve common problems. These patterns help the programmer to make the code more stable, that is, it can be easily managed over a long period and in the face of changes and development.

These patterns are generally divided into three categories:

  • Structural Design Patterns help define the relationships between components by defining a simpler method.
  • Creative Design Patterns are used to create objects suitable for a specific situation.
  • Behavioral Design Patterns highlight common examples of communication between objects in JavaScript.

2. Explain the difference between Prototypal and Classical types of inheritance.

There are two main types of inheritance in programming: classical inheritance and prototypic inheritance.

Classic inheritance: In this type of inheritance, objects are created from classes. For example, “Car” is an object of the “Vehicles” class and inherits from it. In other words, objects are special instances of a class.

Prototypic inheritance: This type of inheritance works differently. In prototypic inheritance, any object can be copied from another object, even if they do not inherit from the same class. That is, an object can act as a template for other objects without inheriting from a specific class.

3. What is meant by Object Destructuring?

Destructuring is a feature in JavaScript. It allows the programmer to easily extract the information contained in an object or an array. This feature was introduced in JavaScript with the release of the ES6 standard.

4. Explain WeakSet in JavaScript.

WeakSet in JavaScript is a data type that is used to store a collection of unique and ordered objects. WeakSet works like Set, but with a few important differences:

  • WeakSet only holds objects and does not accept other data types such as numbers or strings.
  • The relationship between the objects in the WeakSet is weak. That is, if no reference points to an object in the WeakSet, this object may be deleted by the JavaScript memory management mechanism (Garbage Collector).
  • WeakSet has only three methods: “add()” to add an object to the set, “delete()” to remove an object, and “has()” to check if an object exists in the set.

5. What are generator functions?

Generator functions in JavaScript are a special type of function that was introduced in the ES6 version. One of the properties of generator functions is that they can stop during execution and then continue from where they left off. Generator functions are defined using the `function*’ keyword instead of the usual `function’.

Another difference between generator functions and normal functions is that in the normal function, the “return” keyword is used to return a value, and as soon as the “return” command is executed, the execution of the function stops. But generator functions don’t execute code when called. Rather, they return a generator object that controls the execution of the code. The generator object contains a method called “next()”. When this method is called, the code is executed until the nearest `yield’ statement and the `yield’ value is returned.

6. How many ways to create an object in JavaScript?

In JavaScript, we can create or define objects in several different ways:

  • Object: We create an object by using the “Object” keyword.
  • Using Class: This method allows the programmer to create objects with specific properties and functions.
  • create() method: The create() method added to the original object can be used to create a new object.
  • Object Literal: We can easily create objects using literals (such as `{}’ for objects and `[]’ for arrays). This method allows direct creation and definition of object properties.
  • Function usage: Functions can be used like factories to create objects. This method allows the creation of objects with certain characteristics.
  • Object Constructor: Object constructor functions are functions that are created using the `new’ keyword and create a new object with specified properties.

7. Why callbacks are used in JavaScript programming?

In JavaScript programming, using a callback you can say “do A, when it’s done, do B, and after B, do C, and so on.” In this way, each task is executed only when the previous task is finished.

The main use of callbacks in JavaScript is to allow developers to write code that executes concurrently and logically, reacting to events and time-consuming operations. Callbacks can be used to handle operations whose time is unknown (such as network requests or waiting for a user response).

For example, using callbacks, HTTP requests are sent to the server, and when the response is received from the server, the response code is executed. This application is very important in the development of web applications. Because without blocking the execution of the code, we can access server data simultaneously with several other operations.

8. What is a Temporal Dead Zone?

Temporal Dead Zone (TDZ) is a condition in JavaScript where when `let’ and `const’ are used to define variables, it is impossible to access the variables before they are initialized. In other words, variables cannot be accessed until they are defined, which may lead to execution errors. Such a situation where access to the variable is not possible is called a Temporal Dead Zone.

9. What is the role of deferred scripts in JavaScript?

When a user opens a web page, the browser starts loading the content of that page. This content includes text, images, and JavaScript codes. If there are many or complex JavaScript codes on the web page, it will take time to load and execute them. This causes a delay in displaying the page to the user.

Deferred scripts serve as an optimal way to manage scripts. In this case, instead of immediately executing page codes, other page content such as text and images are loaded first, and then JavaScript scripts are executed. In this way, page content is quickly displayed to the user and scripts cannot delay the page loading process.

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