kingsubin

1. String concatenation

console.log('my' + ' cat'); // my cat
console.log('1' + 2); // 12
console.log(`string literals: 1 + 2 = ${1 + 2}`); // 1 + 2 = 3

 

 

2. Numeric operators

console.log(1 + 1); // add : 2
console.log(1 - 1); // substract : 0
console.log(1 / 1); // divide : 1
console.log(1 * 1); // multiply : 1
console.log(5 % 2); // remainder : 1
console.log(2 ** 3); // exponentiation : 8

 

 

3. Increment and decrement operators

let counter = 2;
const preIncrement = ++counter; // 3, 3
const postIncrement = counter++; // 3, 4
const preDecrement = --counter; // 3, 3
const postDecrement = counter--; // 3, 2 

 

 

4. Assingment operators

let x = 3;
let y = 6;
x += y;
x -= y;
x *= y;
x /= y;

 

 

5. Comparison operators

console.log(10 < 6); // less than
console.log(10 <= 6); // less than or equal
console.log(10 > 6); // greater than
console.log(10 >= 6); // greater than or equal

 

 

6. Logical operators : || (or), && (and), ! (not)

const value1 = true;
const value2 = 4 < 2;

// || (or), finds the first truthy value
console.log(`or: ${value1 || value2 || check()}`); // true

// && (and), finds the first fals value
console.log(`and: ${value1 && value2 && check()}`); // false

// often used to compress long if-statement
// nullableObject && nullableObject.something
if (nullableObject != null) {
	nullableObject.something;
}

function check() {
	for (let i = 0; i < 10; i++) {
		// wasting time
		console.log('kingsubin');
	}
}

// ! (not)
console.log(!value1); // false

 

 

7. Equality

const stringFive = '5';
const numberFive = 5;

// == loose equality, with type conversion
console.log(stringFive == numberFive); // true
console.log(stringFive != numberFive); // false

// === strict equality, no type conversion
console.log(stringFive === numberFive); // false
console.log(stringFive !== numberFive); // true

// object equality by reference
const ellie1 = { name: 'ellie' };
const ellie2 = { name: 'ellie' };
const ellie3 = ellie1;
console.log(ellie1 == ellie2); // false
console.log(ellie1 === ellie2); // false
console.log(ellie1 === ellie3); // true

// equality - puzzler
console.log(0 == false); // true
console.log(0 === false); // false
console.log('' == false); // true
console.log('' === false); // false
console.log(null == undefined); // true
console.log(null === undefined); // false

 

 

8. Conditional operators : if, else if, else

const name = 'ellie';
if (name === 'ellie') {
	console.log('Welcome, Ellie!');
} else if (name === 'coder') {
	console.log('You are amazing coder');
} else {
	console.log('unkwnon');
} // Welcome, Ellie!

 

 

9. Ternary operator : ?

console.log(name === 'ellie' ? 'yes' : 'no');

 

 

10. Switch statement

// use for multiple if checks
// use for enum-like value check
// use for muliple type checks in TS
const browser = 'IE';
switch (browser) {
	case 'IE' :
		console.log('go away');
		break;
	case 'Chrome' :
	case 'Firefox' :
		console.log('love u');
		break;
	default:
		console.log('same all');
		break;
} // go away

 

 

11. Loops

// while loop, while the condition is truthy,
// body code is executed.
let i = 3;
while (i > 0) {
	console.log(`while: ${i}`);
	i--;
} // 3 2 1

// do while loop, body code is executed first,
// then check the condition.
do {
	console.log(`do while: ${i}`);
	i--;
} while (i > 0); // 0

// for loop, for (begin; condition; step)
for (i = 3; i > 0; i--) {
	console.log(`for: ${i}`);
} // 3 2 1 

for (let i = 3; i > 0; i = i - 2) {
	// inline variable declaration
	console.log(`inline variable for: ${i}`);
} // 3 1

// nested loops
for (let i = 0; i < 10; i++) {
	for (let j = 0; j < 10; j++) {
		console.log(`i: ${i}, j: ${j}`);
	}
}

// break, continue
// Q1. iterate from 0 to 10 and print only even numbers (use continue)
for (let i = 0; i < 11; i++) {
	if (i % 2 !== 0) {
		continue;
	}
	console.log(`q1. ${i}`);
}

// Q2. iterate from 0 to 10 and print numbers until reaching 8 (use break)
for (let i = 0; i < 11; i++) {
	if (i > 8) {
		break;
	}
	console.log(`q2. ${i}`);
}

 

 

 

 

 

 

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