Logical operator me 2 se adhik logic rahne par,left to right jaye.

Truthy & falsy

Everything in JS is true or false (in boolean context).
This doesn't mean their value itself is false or true, but they are treated as false or true if taken in boolean context.
Falsy values
false, 0, -0, On (Biglnt value),""(empty string) ,null, undefined, NaN
Truthy values
Everything else

Alert & Prompt

Alert displays an alert message on the page.
alert("something is wrong!");

Prompt displays a dialog box that asks user for some input.
prompt("please enter your roll no.")


String Methods

Methods - actions that can be performed on objects. //same like function

Format
stringName.method( )

String are Immutable in JS
No changes can be made to strings.
Whenever we do try to make a change, a new string is created and old one remains same.
only first occurence replaceble in slice.

Array (Data Structure)

Linear collection of things.
but string are immutable.
concat karne pay naya array me sabko dal deta hai, mtb primary array ka value abhi bhi wahi hai. lets check it......
slice and splice me difference - slice me array copy hota ha, but splice me original array me hi remove,replace ho jata hai.
ye khali pahala letttere wise sort karta ha
ye normal variable ki tarah array contant treat nahi karega, es const array me push,pop sab kar sakte ha but esko pura nahi badal sakte ha. ex- arr[1,2,3,4]; es tarah naya addres nahi dal sakte hai.

conclusion- const lagane ke bad array ka address nahi change kar sakte hai ,bus value change kar sakte hai. Ye hai array refference ka locha