Rest parameters and Arguments | JavaScript

[evanc]

I have been coding with JS for 4 years and I had no idea that you could do this. So incredibly useful, thank you!

[techwithsaket]

First time I am saying thanks to any youtuber. Thanks a lot.

[kshitijnegi]

Its good to learn JS from Telusko as you get to know how he also compares the syntax with JAVA and other languages.

[-UPH-KRISHNAM]

There is variable length arguments in python too sir, we use *args

[ewlgirl]

I have watched many video regarding this, sir, you are awesome, i got this concept easily

[TinyMaths]

Just discovering your channel. Thanks for the clear explanation. I was just covering this on the FreeCodeCamp curriculum.
Nice video background by the way.

[MuuoMuumbi]

Thanks a lot, sir, and I think the other language you are talking about which uses args is Python, (args and kwargs)

[gbbarn]

Good video! although you forgot to mention that you could rename your rest parameters, instead of ...args you could define it as ...extraElements, for readability sake, one should always do.

[et-mental-]

Don't you think this is more efficient:

function sum(...args) {
let sum = 0;

for(let i = 0; i < arguments.length; i++)
sum = sum + arguments[i];

return sum;
}

[Mokhtarmrt]

What is the difference between these 2 codes as the result is the same:

function sum(a, b){
return a+b;
}
let result sum(4, 5);
console.log(result);

AND

function sum(a, b){
return a+b;
}
console.log(sum(4, 5));

When should i declare a variable and when not? because i saw many of your videos and you declare variables everywhere without telling why we need to declare them.
When should i use a variable in javascript and when not?