Java is a widely used programming language famous for creating enterprise, web, and mobile applications. Java is also used for creating server-side applications, desktop applications, and games. Java interview questions can cover various topics, from basic programming concepts to advanced Java frameworks.
Check here our top 25 Javascript Interview Questions and Answers:
JavaScript is a high-level, object-oriented programming language. Its features include dynamic typing, first-class functions, event-driven programming, and prototypal inheritance.
Undefined means a variable has been declared but has not yet been assigned a value, while null is an assignment value that represents no value or no object.
“==” compares the value of two operands, while “===” compares the value and data type of the operands.
Hoisting is a mechanism in JavaScript where variables and function declarations are moved to the top of their respective scopes during the compilation phase.
A closure is a function that has access to the variables in its outer part, even after the external process has returned.
A function declaration is hoisted to the top of its scope and can be called before it is defined, while a function expression is not boosted and can only be called after it has been determined.
The “This” keyword refers to the object of which the function is a method.
There are several ways to create an object in JavaScript, including object literals, constructor functions, and the Object.create() method.
Event bubbling is a process in which an event is triggered on a child element and then bubbles up through the parent elements in the DOM tree until it reaches the document object.
“Let” is block-scoped, while “var” is function-scoped. This means that variables declared with “let” are only accessible within the block defined in, while variables declared with “var” are accessible within the entire function they were limited in.
A callback function is a function that is passed as an argument to another position and is executed after that function has been completed.
Synchronous programming executes code sequentially, while asynchronous programming allows code to run concurrently.
The “prototype” property is a mechanism in JavaScript that allows objects to inherit properties and methods from their parent objects.
The “bind” method creates a new function with a specified “this” keyword and any arguments passed to it.
“Slice” creates a new array that contains a portion of the original array, while “splice” modifies the original collection by removing or adding elements to it.
The “spread” operator allows an iterable object, such as an array or a string, to be expanded into individual elements.
“Map” creates a new array with the results of calling a function on each element of the original collection, while “forEach” executes a process on each part of the original array.
The “Promise” object is a mechanism in JavaScript that allows asynchronous operations and returns a value once the process is complete.
JavaScript supports several types of operators, including arithmetic operators (+, -, *, /), comparison operators (>, <, >=, <=), logical operators (&&, ||, !), assignment operators (=, +=, -=, *=, /=), and others.
Var is function-scoped, while let and const are block-scoped. Var can be redeclared and reassigned, let can be reassigned but not redeclared, and const cannot be reassigned or redeclared.
A closure is a function that has access to the variables defined in its outer scope, even after that scope has closed.
The event loop is a mechanism that allows JavaScript to perform non-blocking I/O operations. It handles events and callbacks and ensures that the execution of JavaScript code never blocks the main thread.
Asynchronous programming in JavaScript involves executing code without blocking the main thread. This is typically done using callbacks, promises, or async/await.
The ‘this’ keyword refers to the object currently executing the function. Its value depends on how the process is called and can be changed using the call(), apply(), and bind() methods.
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