js mcq interview

Author: nilajcoder

Linkdin Post/Js/condition.js

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+if([]){
+    console.log("Nilaj is Absent")
+}else{
+
+    console.log("Nilaj is Present")
+}
+
+
+if([]==true){
+    console.log("Nilaj is Absent")
+}else{
+
+    console.log("Nilaj is Present")
+}
+
+
+
+
+
+
+
+/*
+let obj = {
+    a: {
+        b: undefined
+    }
+}
+
+console.log(obj?.a?.b?.c?.d ? "jithin" : "nilaj");//nilaj
+
+
+var abc = 25;
+if (function f() {}) {
+    abc = abc + typeof f;
+}
+
+console.log(abc);//25undefined
+*/

Linkdin Post/Js/equal.js

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+
+
+
+/*
+
+ Difference between == and ===?
+
+    == checks for value equality, while === checks for both value and type equality.
+    == will perform type coercion if the types are different, while === will not.
+*/
+
+
+console.log(1 == "1") // true
+console.log(1 === "1") // false
+
+
+console.log(typeof NaN ==="number")//true
+
+
+
+let a=["1","2","3"]
+console.log(a.indexOf("2"))

Linkdin Post/Js/forinof.js

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+
+// for..in loop
+// The for..in loop is used to iterate over the properties of an object.
+const person = {
+    name: "John",
+    age: 30,
+    city: "New York"
+};
+
+for (let i in person) {
+    console.log(person[i]);
+}
+
+
+// for..of loop
+// The for..of loop is used to iterate over iterable objects like arrays, strings, etc.
+var numbers = [1, 2, 3];
+var sum = 0;
+for (let i of numbers) {
+    //console.log();
+        sum += i;
+
+}
+console.log("Sum is " + sum);

Linkdin Post/Js/funmcq.js

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+
+function xyz(a, b, c) {
+
+}
+console.log(xyz.length)//3
+function abc(x = 0, y, z) {
+
+}
+console.log(abc.length)//0
+function pqr(d, e = 0, f) {
+
+}
+console.log(pqr.length)//1
+function sef(y, z, b = 0) {
+
+}
+
+console.log(sef.length)//2
+function def(y = 0, x = 0, z = 0) {
+
+}
+console.log(def.length)//0
+
+
+
+

Linkdin Post/Js/mcq.js

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+
+console.log([1,2,3]+[4,5,6]); // [1,2,34,5,6] - concatenation of two arrays
+
+console.log("1,2,3" + "4,5,6")
+
+console.log([1,2,3] - [4,5,6])// NaN
+
+console.log(1+"1"-1)// 10
+
+let x=1;
+let y="1"
+console.log(x==y) // true
+console.log(x===y) // false
+
+
+console.log(typeof NaN ==="number") // type``of NaN is number is string ==="strtring" // true
+console.log(typeof[])// object
+
+/*what is spread operator
+ Spread operator is used to expand an iterable (like an array) into its individual elements.
+It is denoted by three dots (...).
+*/
+function foo(){
+    return;
+    {
+       bar : "hello";
+
+    }
+}
+console.log(foo()) // undefined
+
+/*
+Which of this looping structure is not supported in JavaScript?
+1. for..in
+2. for..of
+3. for..each
+4. for..loop
+Answer: 3. for..each
+*/
+
+/* const can not be updated or re-declared within the same scope.
+const a=20;
+a=30; // TypeError: Assignment to constant variable.
+
+
+
+
+14. What is a promise in JavaScript?
+A) A function that always returns true
+B) A value that may be available now, later, or never
+C) A global object for HTTP requests
+D) A variable that can't be changed
+
+Answer: B) A value that may be available now, later, or never
+*/
+
+console.log(typeof null) // object
+
+let a={}
+let b=a
+a.name="JS"
+console.log(b.name)// JS
+
+/*
+let is a block-scoped variable declaration keyword in JavaScript.
+let can be updated
+but not re-declared within the same scope.
+*/
+let arr=[1,2,3];
+arr.length=0;
+console.log(arr) // [] - empty array
+
+
+const c = [1, 2];  
+const d= [1, 2];  
+console.log(JSON.stringify(c) === JSON.stringify(d));// true
+// JSON.stringify() converts a JavaScript object or value to a JSON string.

Linkdin Post/Js/trun.js

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+function print(x){
+    console.log(~x)
+}
+
+print(2.8)
+print(2.1)
+print(2.9)
+print(6.25)
+print(0.25)
+print("-25.56")

Linkdin Post/Js/typeof.js

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+
+
+let x
+console.log(typeof x)
+
+let y=10
+console.log(typeof y)
+
+let z=10.25
+console.log(typeof z)
+
+let a=true
+console.log(typeof a)
+
+let b="nilaj"
+console.log(typeof b)
+
+let c=null
+console.log(typeof c)
+
+let d=BigInt(8)
+console.log(typeof d)
+
+let e=Symbol("hi")
+console.log(typeof e)