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Advanced JS

Function Expression vs Function statement vs IIFE​

iffe (xyz()) is same as ((xyz)())​

THIS​

When 'This' is defined in object, it refers to object's env & everywhere else it refers to global variable​

  • but but but if function is inside an object, it again refers to global this
  • so output updated c objectupdated c object
  • to resolve above problem put this = self above console.log Below is an screenshot

Functions are first class members in JS​

Functions are plain JS objects with added superpowers : it can do allobject things +​

  • the code you write inside fun sits in a special property called 'code' which is invocable - meaning , will have an execution context
  • when we call fun() -> it invokes the code we have written
  • it has an optional name property to distinguish from other functions

Coercion​

console.log(3<2<1) \\true Why?

  • Coz if you see above table it starts reading from ltr in case of < & >
  • so it meas it will be evaluated as (3<2) <1 , 3<2 == false , so false <1 ,
  • Coercion takes place here meaning Number(false) <1=> 0 <1 ==> True

Operator Precedence​

a+b*c/d : Precendence is decided by below table​

Answer: 4,4,4 This happens because of precedence. it goes from right to left. if precedence was from LtoR answer would be 2,2,2

View All precedence here MDN​

Notations​

+( 3, 4) //Pre fix notation​

( 3, 4)+ //Post fix notation​

3 + 4 // In fix notation - JS makes it eaasy for us to write code in this way using In fix notation​

Async Functioning​

Async Functioning

In the above code, when clicked immediately after page reload, result is below:

Async Functioning

🤔 Reason?

JS first finish processing || Stack and then goes to queue =

so all the events like clicks etc are placed in queue and js takes times to finish all execution context (functions) and then go to queue.

Objects & Functions​

  • Both are same