javascript/LogicalJsQuestions.txt at master · springapidev/javascript · GitHub

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Logical Questions:
1. What will the code below output to the console and why ?

console.log(1 +  "2" + "2");
console.log(1 +  +"2" + "2");
console.log(1 +  -"1" + "2");
console.log(+"1" +  "1" + "2");
console.log( "A" - "B" + "2");
console.log( "A" - "B" + 2);

2. What will be the output of the following code:

for (var i = 0; i < 5; i++) {
	setTimeout(function() { console.log(i); }, i * 1000 );
}


3. What will be the output when the following code is executed? Explain.

console.log(false == '0')
console.log(false === '0')


4. What will the following code output to the console:

console.log((function f(n){return ((n > 1) ? n * f(n-1) : n)})(10));

5. What do the following lines output, and why?

console.log(1 < 2 < 3);
console.log(3 > 2 > 1);

6. Imagine you have this code:

var a = [1, 2, 3];

a) Will this result in a crash?

a[10] = 99;

b) What will this output?

console.log(a[6]);

7. What is the value of typeof undefined == typeof NULL?

8 What would following code return?

console.log(typeof typeof 1);


9. What will the following code output and why?

var b = 1;
function outer(){
   	var b = 2
    function inner(){
        b++;
        var b = 3;
        console.log(b)
    }
    inner();
}
outer();


10. Writer a array with 3 elements and add new one at the end of array and another new one at the begining of the array.


============= True False===========

11. Is 'false' is false?


12. Is ' ' is false?


13. What about {}?


14. Tell me about []?


15. You talked bout '' to be falsy. What about new String('')?


16. Tell me about new Boolean(false)


17. Boolean(function(){})


18. Boolean(/foo/)


19. true%1


20. ''%1