Guess Output of JS programs
📄 Table of contents
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var str = new String("anil");
console.log(typeof str);var str1 = "anil";console.log(typeof str1);
console.log(str == str1); # type-coersion takes place here
console.log(str === str1);#Output:
"object"
"string"
true
false// IIFE
(function(){
let a = b = 100;
})();console.log(b);
console.log(a); // 100
// "ReferenceError: a is not defined// IIFE
(function(){
var b = 101;
let a = 100;
})();console.log(b);
console.log(a); // "ReferenceError: b is not defined "
// will not reach here
Post increment will return your value before incrementing thats why we are getting 0 all the times. We should use ++num which will return after incrementing and will output 1,2,3.
LogMeIn
const a = [1,2,3];
const b = [1,2,3];
const c = “1,2,3”;console.log(a === b); // false
console.log(a === c); // false// convert [1,2,3] to String
[1,2,3] + ""// "1,2,3"▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬var a = 1;
function b() {
a = 10;
return;
function a() {}
}
b();# undefined▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬function parent() {
var hoisted = "a variable";
function hoisted() {
return "a function";
}
return hoisted();
}
console.log(parent());Output: # TypeError: hoisted is not a functionVariable assignments > function declarations > variable declarations▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬function containingFunction() {
var hoistedVariable = 2 + 2;
function hoistedFunction() {
return hoistedVariable;
}
return hoistedFunction();
}
containingFunction()# 4
▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬▬let arr = [4, 4];for (x of arr){
console.log(x);
}// output => 4,4for (x of arr.keys()) {
console.log(x); // output = 🤔 ?
}// output => 0,1
The above code will output the following to the console:
outer func: this.foo = bar
outer func: self.foo = bar
inner func: this.foo = undefined
inner func: self.foo = bar(function () {
var a = 4;
function f1() {
var a = 5;
}
if (true) {
var a = 6;
}
f1();
console.log(a);
})()# 6function Base2() {
this.num = 2;
}
Base2.prototype = {
base_get_num: function () {
return this.num;
}
}
function Derived2() {}
Derived2.prototype = Base2.prototype;
var d = new Derived2();
console.log(d.base_get_num());# undefinedfunction Base2() {
this.num = 2;
}
Base2.prototype = {
num: 4,
base_get_num: function () {
return this.num;
}
}function Derived2() { }
Derived2.prototype = Base2.prototype;var d = new Derived2();
console.log(d.base_get_num());# 4function Base3() {
this.num = 2;
}
Base3.prototype = {
num: 4,
base_get_num: function () {
return this.num;
}
}
function Derived3() {
Base3.apply(this, arguments);
}var d = new Derived3(2);function bar(){
return foo;
foo =10;
var foo = "11";
function foo() {}
}
alert(typeof bar()); # function
Shallow Copy:
const a = { foo: {bar: 1 }}
const b = Object.assign({}, a)
// get a clone of a which you can change with-out modifying a itselfb.foo.bar = "999";
console.log(a.foo.bar);
# 999const orig = { foo:
{bar: 1}
}; // nested objectconst copy = {...orig}; // get a clone of orig which you can change with out modifying
orig itselfcopy.foo.bar = "999";
console.log(orig.foo.bar); # "999"
Object.create()
(function(x) {
return (function(y) {
console.log(x);
})(2)
})(1);# 1(function () {
try {
throw new Error();
} catch (x) {
var x = 1, y = 2;
console.log(x);
}
console.log(x);
console.log(y);
})();# 1
# undefined
# 2
SetTimeout Exercise()
console.log("1");
setTimeout(() => console.log("2"),0);
console.log("3");
Promise.resolve(console.log("4"));#
1
3
4
2console.log("1");
setTimeout(() => console.log("2"),0);
Promise.resolve(console.log("4"));
console.log("3");#
1
4
3
2(function(x) {
return (function(y) {
console.log(x);
})(2)
})(1);# output:
1(function () {
try {
throw new Error();
}
catch (x) {
var x = 1, y = 2;
console.log(x);
}
console.log(x);
console.log(y);})();# output:
1
undefined
2function f1(arr) {
arr.push(7);
}
function f1(arr) {
arr.push(8);
}var arr = [6];
f1(arr);
console.log(arr.join(","));# 6,8var count1 = 0, count2 = 0;
for (var i = 0; i < 3; i++) {
try {
if (i === 2) {
console.log("inside try statement");
}
}
catch (e) {
count1++;
}
finally {
count2++;
}
}
console.log(count1, count2);# inside try statement
# 0 3
