Interview Questions

Interview Questions?

Q. You might have a form created in your React App that user might try to close by closing the tab, reloading the page or close the browser directly without saving the data (or submitting the form). You might want to prompt the user in this case to alert them that there might be unsaved changes that might be lost.

How to do that in React ?

Answer @ https://inthetechpit.com/2020/05/19/prompt-user-with-beforeunload-on-browser-tab-close-react-app/

Q. You have a form…in one child component C1…you want to fetch only input type=”text” elements, in 2nd child component C2…you want to fetch only radio elements… in 3rd child component C3…you want to fetch only checkboxes elements.

How would you proceed on this ?

Guess

var result = [];
    for(var i=0; i< 10; i++){
      result.push(i);
}
console.log(result);
#[0, 1, 2, 3, 4, 5, 6, 7, 8, 9];
var result = [];
   for(var i=0; i< 10; i++){
      result.push(function(){
        return i
     });
   }
console.log(result[1]());
#10
var x = 20;
var y= 21;
delete x;
delete y;
console.log(window.x);
console.log(window.y); 
#20
21
var fn = "A";
var fln = "B";
function getName(){
 var fn = "C";
 var fln = "D";
}
getName();
console.log(fn);
console.log(fln);
#
A
B

Problem Statement

Identify the pattern and output:

[‘A’,’B’,’C’,’D’]

1->A
4->D
5->AA

6->ab

7->ac
8 -> AD
9->BA
12->BD
13->CA

17-> aaaa

???? -> AAAB

— — — — — — — — — — —

Reverse a string without affecting special characters

Input => abc.de.f.g

Expected Output => gfe.dc.b.a

Input:   str = "a,b$c"
Output:  str = "c,b$a"
Note that $ and , are not moved anywhere.  
Only subsequence "abc" is reversed

Input:   str = "Ab,c,de!$"
Output:  str = "ed,c,bA!$"

Solution: https://www.geeksforgeeks.org/reverse-a-string-without-affecting-special-characters/

Observer Design Pattern vs pub-sub pattern

@ https://medium.com/easyread/difference-between-pub-sub-pattern-and-observable-pattern-d5ae3d81e6ce

difference between let and const