The concept of creating a single function or method that can operate on multiple types of objects is known as _________.
- Overloading
- Inheritance
- Polymorphism
- Abstraction
The concept of creating a single function or method that can operate on multiple types of objects is known as "Polymorphism." In JavaScript, polymorphism can be achieved through method overriding and dynamic method binding, enabling different objects to respond to the same method in a way that suits their specific type.
During a job interview, you're asked about the evolution of JavaScript. The interviewer specifically wants to know about a major shift in JavaScript's usage from merely adding interactivity to web pages to being used in server-side programming. What technology or platform brought about this shift?
- Node.js
- Apache Tomcat
- PHP
- Ruby on Rails
JavaScript's major shift into server-side programming was largely enabled by Node.js. Node.js is a runtime environment that allows JavaScript to be executed on the server, making it suitable for building scalable, server-side applications. It revolutionized web development by unifying front-end and back-end languages.
Why might for...of loops be preferred when working with asynchronous code?
- They can be used with any iterable object.
- They automatically handle Promise resolution.
- They are faster than traditional for loops.
- They provide better error handling mechanisms.
For...of loops are preferred when working with asynchronous code because they automatically handle Promise resolution. When you iterate over an iterable that contains Promises, for...of will await each Promise and provide the resolved value, making it more convenient for working with asynchronous operations.
What is the primary difference between while and do-while loops in JavaScript?
- The while loop always executes the code block at least once
- The do-while loop is more efficient
- The while loop is not suitable for iterating over arrays
- The do-while loop doesn't have a condition
The primary difference is that in a while loop, the condition is checked before executing the code block. If the condition is initially false, the code block may never run. In contrast, the do-while loop guarantees that the code block is executed at least once because it checks the condition after executing the block. This makes do-while useful when you want the code to run once before checking the condition.
The ________ operator can be used to compare both value and type in JavaScript.
- Equality (===)
- Assignment (=)
- Identity (==)
- Inequality (!=)
The Equality (===) operator can be used to compare both value and type in JavaScript. It checks if two values are strictly equal, meaning they have the same value and the same data type. The other options, such as Assignment (=) and Identity (==), do not perform strict value and type comparison. Inequality (!=) checks for inequality.
The process of an object inheriting properties and behaviors (methods) from its prototype is known as _________.
- Encapsulation
- Inheritance
- Polymorphism
- Abstraction
Inheritance is the process by which an object inherits properties and behaviors (methods) from its prototype or parent object. JavaScript uses a prototype-based inheritance model, where objects inherit from other objects, and this is a fundamental concept in the language.
The ________ method is used to read a Response stream and return it as a blob.
- text()
- json()
- blob()
- arrayBuffer()
The blob() method is used to read a Response stream and return it as a blob object. This is commonly used when dealing with binary data or files. The other options (text(), json(), arrayBuffer()) are used for different types of Response data processing.
You are debugging a web application and notice that a "for" loop is causing the webpage to hang. What could be a potential reason and how might you solve it?
- Infinite Loop
- Excessive DOM Manipulation
- Missing Loop Condition
- Insufficient Memory Allocation
One potential reason for a webpage hang caused by a "for" loop is excessive DOM manipulation within the loop, which can block the main thread. To solve this, consider moving DOM manipulation outside the loop or optimizing the DOM operations. An infinite loop, missing loop condition, or insufficient memory allocation could also cause hangs but are less likely in this context. JavaScript Debugging
What is lexical scoping in JavaScript?
- A type of error handling in JavaScript
- A scoping mechanism in JavaScript
- A method to declare global variables
- A JavaScript data type
Lexical scoping in JavaScript refers to the way variable scope is determined by the placement of variables in the source code. Variables declared inside a function are accessible within that function, creating a hierarchy of scope. This helps prevent variable conflicts and promotes clean code.
If an array arr has a length n, executing arr.push(x) will set arr[_______] equal to x.
- arr.length - 1
- arr.length + 1
- arr.length
- arr.length - 2
When you use arr.push(x), it appends the element x to the end of the array and increases the length property of the array by 1. Therefore, the new element will be at the index arr.length - 1, which is one less than the new length. For example, if arr has a length of 5, arr.push(x) will add x at index 4.