Interview Questions

What is DOM?

What is Event loop = run time model present in the Javascript engine

What is hoisting in Javascript?

Where are let/const declarations are hoisted?

Functions Expressions and Arrow functions are not hoisted, because they behave like any other variable and a special keyword 'undefined' is stored in them, Only regular functions are hoisted

What is a closure?

What is callback hell - make code unreadble and unmaintainable

Map, Filter, Reduce - are High order functions for an array

How many scopes in javascript?

Call, Bind and Apply - function borrowing

What is this keyword?

Arrow vs normal function?

What is memozation?

rest and spread operators?

What would below code output in console?

let arr = [1,2,3,4,5];
let obj = { ...arr };

console.log(obj);

What would below code block output?

const arr = [3,4,5,6]
arr.foo = 'Hi';

for (let i of arr) {
 console.log(i)
}

for (let i in arr) {
 console.log(i)
}

What is the difference between == and === in JavaScript?

== performs type coercion, meaning it converts the operands to the same type before making the comparison, while === does not perform type coercion and returns false if the operands have different types.

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