Front-end-Developer-Interview-Questions/src/questions/javascript-questions.md

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JavaScript Questions	layouts/page.njk	/questions/javascript-questions/index.html

• Explain event delegation.
• Explain how this works in JavaScript.
  • Can you give an example of one of the ways that working with this has changed in ES6?
• Explain how prototypal inheritance works.
• What is the difference between a variable that is: null, undefined or undeclared?
  • How would you go about checking for any of these states?
• What is a closure, and how/why would you use one?
• What language constructions do you use for iterating over object properties and array items?
• Can you describe the main difference between the Array.forEach() loop and Array.map() methods and why you would pick one versus the other?
  • Сan you describe other popular methods for iterating over arrays?
• What is a typical use case for anonymous functions?
• What is the difference between host objects and native objects?
• Explain the difference between: function Person(){}, var person = Person(), and var person = new Person()?
• Explain the differences on the usage of foo between function foo() {} and var foo = function() {}
• Can you explain what Function.call and Function.apply do? What is the notable difference between the two?
• Explain Function.prototype.bind.
• What is the difference between feature detection, feature inference, and using the UA string?
• Explain "hoisting".
• What is type coercion? What are common pitfalls of relying on type coercion in JavaScript code?
• Describe event bubbling.
• Describe event capturing.
• What is the difference between an "attribute" and a "property"?
• What are the pros and cons of extending built-in JavaScript objects?
• What is the difference between == and ===?
• Explain the same-origin policy with regards to JavaScript.
• Why is it called a Ternary operator, what does the word "Ternary" indicate?
• What is strict mode? What are some of the advantages/disadvantages of using it?
• What are some of the advantages/disadvantages of writing JavaScript code in a language that compiles to JavaScript?
• What tools and techniques do you use debugging JavaScript code?
• Explain the difference between mutable and immutable objects.
  • What is an example of an immutable object in JavaScript?
  • What are the pros and cons of immutability?
  • How can you achieve immutability in your own code?
• Explain the difference between synchronous and asynchronous functions.
• What is event loop?
  • What is the difference between call stack and task queue?
• What are the differences between variables created using let, var or const?
  • Can you change a property of an object defined via const? How you can change this behavior?
• What are the differences between ES6 class and ES5 function constructors?
• Can you offer a use case for the new arrow => function syntax? How does this new syntax differ from other functions?
• What advantage is there for using the arrow syntax for a method in a constructor?
• What is the definition of a higher-order function?
• Can you give an example for destructuring an object or an array?
• Can you give an example of generating a string with ES6 Template Literals?
• Can you give an example of a curry function and why this syntax offers an advantage?
• What are the benefits of using spread syntax and how is it different from rest syntax?
• How can you share code between files?
• Why you might want to create static class members?
• What is the difference between while and do-while loops in JavaScript?
• What is a promise? Where and how would you use promise?
• Discuss how you might use Object Oriented Programming principles when coding with JavaScript.
• What is the difference between event.target and event.currentTarget?
• What is the difference between event.preventDefault() and event.stopPropagation()?

Coding questions

• Make this work:

duplicate([1,2,3,4,5]); // [1,2,3,4,5,1,2,3,4,5]

• Create a for loop that iterates up to 100 while outputting "fizz" at multiples of 3, "buzz" at multiples of 5 and "fizzbuzz" at multiples of 3 and 5
• What will be returned by each of these?

console.log("hello" || "world")
console.log("foo" && "bar")

• Write an immediately invoked function expression (IIFE)