Most asked code snippets in Javascript Interview

Vineet Mishra
3 min readFeb 1, 2022

Hi awesome people, I hope you are doing fine, let's roll out code snippets

Q1. Guess the Output :

var a =1
var b =’1'

console.log(a===b);
console.log(a==b);

take a breath and give a thought what would be the output, think hard before jumping into output

output:
false
true

Reason: In “===” it with compare datatype also, of LHS & RHS and whereas “==” only compare values of LHS and RHS

Q2. Guess the Output :

let’s do with object

var a= {name:”vineet”}
var b={name:”vineet”}

console.log(a===b);
console.log(a==b);

take a breath and give a thought what would be the output, think hard before jumping into output

Output :
false
false

Reason: When comparing two objects, JavaScript compares internal references which are equal only when both operands refer to the same object in memory, keys, and values are not checked, so the content of the object doesn’t matter, the operands both have to reference the same object to return true in comparison.

Q3. Guess the Output :

setTimeout(()=>{

console.log(“Mishra”)
},2000)

console.log(“Vineet”)

take a breath and give a thought what would be the output, think hard before jumping into output

Output:
Vineet
Mishra

Reason: This happens due to the event loop of javascript, first it will handle synchronous function then after the completion it will handle asynchronous

Q4. Can you write code for this function: sum(a)(b)©….( n)(). This should return the sum of all the numbers a+b+c+..+n.;:

Solutions :

const sum =(a)=>(b)=>(c)=>(d)=>(e)=>()=>a+b+c+d+e

console.log(sum(1)(2)(3)(4)(5)())

Q5. Explain Closures with snippet?

Solutions: A closure gives you access to an outer function’s scope from an inner function

function Outer(){
function Inner(){
console.log(“hello”)
}
return Inner;}

var getValue = Outer
getValue()();

Q6. Guess the output

const arr = [1,2,3,4]

arr.push(5)

take a breath and give a thought what would be the output, think hard before jumping into output

Output: [ 1, 2, 3, 4, 5 ]

Reason: The const declaration creates a read-only reference to a value. It does not mean the value it holds is immutable, just that the variable identifier cannot be reassigned

Q7. Guess the output

const arr = [1,2,3,4]

arr.length =0;

console.log(arr)

take a breath and give a thought what would be the output, think hard before jumping into output

Output : []

Reason: The const declaration creates a read-only reference to a value. It does not mean the value it holds is immutable, just that the variable identifier cannot be reassigned

Q8. How can you call a function as soon as it defines

Solutions:

(function hello()
{ console.log(“hello”)
})();

An IIFE (Immediately Invoked Function Expression) is a JavaScript function that runs as soon as
it is defined. … It is a design pattern which is also known as a Self-Executing Anonymous Function
and contains two major parts: The first is the anonymous function with lexical scope enclosed within
the Grouping Operator ()

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Vineet Mishra

SDE 2 at Accelya , I write about Mobile/Web Development and Deployment, and Interview Q & A