11// 1) What is the output of 10+20+"30" in JavaScript?
22//Ans: 3030 because 10+20 will be 30. If there is numeric value before and after +, it treats as binary + (arithmetic operator).
3-
3+ 44// 2) What is the output of "10"+20+30 in JavaScript?
55// Ans: 102030 because after a string all the + will be treated as string concatenation operator (not binary +).
66
77// 3) Output?
88// Syncronous
99[ 1 , 2 , 3 , 4 ] . forEach ( ( i ) => {
10- console . log ( i )
11- } )
10+ console . log ( i ) ;
11+ } ) ;
1212
1313// Asynchronous
1414function asyncForEach ( array , cb ) {
1515 array . forEach ( ( ) => {
1616 setTimeout ( cb , 0 ) ;
17- } )
17+ } ) ;
1818}
1919
2020asyncForEach ( [ 1 , 2 , 3 , 4 ] , ( i ) => {
2121 console . log ( i ) ;
22- } )
23- 22+ } ) ;
2423
2524// 4) Output? And explain (hint: Octal)
26- console . log ( 016 )
25+ console . log ( 016 ) ;
2726
28- console . log ( 017 )
27+ console . log ( 017 ) ;
2928
30- console . log ( 026 )
29+ console . log ( 026 ) ;
3130
32- console . log ( 027 )
31+ console . log ( 027 ) ;
3332
3433// 5) Output?
35- console . log ( [ ...'Hello' ] ) ;
34+ console . log ( [ ..."Hello" ] ) ;
35+ 36+ // OUTPUT
37+ function sum ( a , b ) {
38+ a = 10 ;
39+ return [ a + b , arguments [ 0 ] + arguments [ 1 ] ] ;
40+ }
41+ 42+ // in "use strict" => [12, 3]
43+ // in normal mood => [12, 12]
44+ console . log ( sum ( 1 , 2 ) ) ;
45+ 46+ // Event Propagation
47+ // event.currentTaget.tagName
48+ // this.tagName
49+ 50+ // sameValuZero algorithm
51+ const sameValueZero = ( a , b ) => {
52+ if ( a === b || ( Number . isNaN ( a ) && Number . isNaN ( b ) ) ) {
53+ return true ;
54+ }
55+ 56+ return false ;
57+ } ;
58+ 59+ // Output
60+ // ==, ===, object.is, sameValuZero algorithm
61+ const array = [ NaN ] ;
62+ 63+ const result = array . includes ( NaN ) ;
64+ console . log ( result ) ; // True: why? => array.includes follows sameValueZero algorithm
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