1. what is template literals

combination of this backtick and $ and {}to write executable code inside a string
a=10
console.log(value of a is ${a})

2. what is hoisting

where var is declared or say hoisted like in js the running happens in 2 phase one is declaration or hoisting other is execution
for var when hoisted if we call we get undefined for const and let we get reference error without assigning value to them

3. var let and const

let and const is block scoped { } and var is function scope so we dont prefer using var use let or const

4. types of datatypes

1. primitive immutable or cannot be modified

• number
• strings
• boolean
• symbol
• undefined - default value provided to variable that has been declare but not assigned any valye
• null - when we declare a value but we dont want to contain any value in it

2. non primitive

• objects - collection of key valye pair
• arrays -
• functions - block of code

5. what is array

• same datatype
• zero index
• group of similar data
• access using index

6. == vs ===

== is equality operator
=== is strict equality operator

example

'5'==5 is true
'5'===5 is false

type coersion

7. what is isnan

check if its not a number
like isNaN('sanskar') is false
like isNaN('123') is true

8. what is null and undefined

null is where we dont wana assign value to variable
undefined is default value assigned to a var without value

9. use of typeof

dtype of typeof(42)

medium module

11. what is map operator

a=[1,2,3,4,5]
double = a.map(n=>n*2)
console.log(a)
console.log(double)

used to create a new array with specific function to each element without mod existing array

12. what is event bubbling and event capturing

event bubbling - model where events are handled from inner most to outermost
event capturing where model events are captured from outermost to innermost

13.what are higher order function

function that can accept another function or return as an argument,
map is a higher order function

14. what is IIFE (Immediately invoked fuction expression)

without being called runs

(fucntion(){
console.log("hell0 world")
})

closures

function that remembers the env in which it was created even after the outer func has finished executing

setTimeout ,setInterval,clearOnterval

let a= 10

const time= setInterval(()=>{

    console.log(a--)

},1000)
setTimeout(()=>{

    clearInterval(time)

},10000)

promises

async task (pending,fullfiled,rejected)

reduce

const num=[1,2,3,4,5]
const sum =num.reduce((acc,curr)=>{
    return acc+curr
})
console.log(sum)