Equality comparisons and sameness

Author: lgope

Interview-Questions/output.js

@@ -1,35 +1,64 @@
 // 1) What is the output of 10+20+"30" in JavaScript?
 //Ans: 3030 because 10+20 will be 30. If there is numeric value before and after +, it treats as binary + (arithmetic operator).
-  
+
 // 2) What is the output of "10"+20+30 in JavaScript?
 // Ans: 102030 because after a string all the + will be treated as string concatenation operator (not binary +).
 
 // 3) Output?
 // Syncronous
 [1, 2, 3, 4].forEach((i) => {
-  console.log(i)
-})
+  console.log(i);
+});
 
 // Asynchronous
 function asyncForEach(array, cb) {
   array.forEach(() => {
     setTimeout(cb, 0);
-  })
+  });
 }
 
 asyncForEach([1, 2, 3, 4], (i) => {
   console.log(i);
-})
-
+});
 
 // 4) Output? And explain (hint: Octal)
-console.log(016)
+console.log(016);
 
-console.log(017)
+console.log(017);
 
-console.log(026)
+console.log(026);
 
-console.log(027)
+console.log(027);
 
 // 5) Output?
-console.log([...'Hello']);
+console.log([..."Hello"]);
+
+// OUTPUT
+function sum(a, b) {
+  a = 10;
+  return [a + b, arguments[0] + arguments[1]];
+}
+
+// in "use strict" => [12, 3]
+// in normal mood => [12, 12]
+console.log(sum(1, 2));
+
+// Event Propagation
+// event.currentTaget.tagName
+// this.tagName
+
+//  sameValuZero algorithm
+const sameValueZero = (a, b) => {
+  if (a === b || (Number.isNaN(a) && Number.isNaN(b))) {
+    return true;
+  }
+
+  return false;
+};
+
+// Output
+// ==, ===, object.is, sameValuZero algorithm
+const array = [NaN];
+
+const result = array.includes(NaN);
+console.log(result); // True: why? => array.includes follows sameValueZero algorithm