JavaScript

Last Updated: 12/14/2022

Operators

  • In JavaScript you have different kinds of operators.
  • You use these operators along with our variables and constants to create expressions and with these expressions you can implement logic and algorithms.
  • In JavaScript you have arithmetic operators, assignment operators, comparison operators, logical operators, and bitwise operators

Arithmetic Operators

  • Arithmetic operators are used for performing calculations, just like the calculations in mathematics
  • Arithmetic operators usually take two operands and then produce a new value.
  • x + y referred as an expression in JavaScript. An expression produces a value.
  • Addition +, Subtraction -, Multiplication *, Division /, Division Remainder/Modulus %, Exponential **, Incremental ++, Decremental --
let  x = 5;
let  y = 2;
console.log(x + y);
console.log(x - y);
console.log(x * y);
console.log(x / y);
console.log(x % y);
console.log(x ** y);

Modulus (%)

  • Division of two integers produces a quotient and a remainder.
  • Result of a modulo operation is the remainder of an arithmetic division.

Increment Operators (++)

  • Based on the position operator will behave differently
  • If you put the increment operator before x (prefix/pre increment) the value of x will be incremented by 1 first and then you will see that on the console
  • If you put this operator after x (posffix/post increment), you will see x on the console first, and then the value of x will be incremented by 1

Pre Increment/Prefix

let x = 5;
let z = ++x;
console.log(z);
console.log(x);

Post Increment/Postfix

let x = 5;
let z = x++;
console.log(z);
console.log(x);

Decrement Operators (--)

  • Based on the position operator will behave differently
  • If you put the decrement operator before x (prefix/pre increment) the value of x will be decremented by 1 first and then you will see that on the console
  • If you put this operator after x (posffix/post increment), you will see x on the console first, and then the value of x will be decremented by 1

Pre Decrement/Prefix

let x = 5;
let z = --x;
console.log(z);
console.log(x);

Post Decrement/Postfix

let x = 5;
let z = x--;
console.log(z);
console.log(x);

Assignment Operators

Assignment Operator

let x = 5

Addition Assignment Operator

x += 2;
equivalent to x = x + 2

Subtraction Assignment Operator

x -= 2;
equivalent to x = x - 2

Multiplication Assignment Operator

x *= 2;
equivalent to x = x * 2

Division Assignment Operator

x /= 2;
equivalent to x = x / 2

Remainder Assignment Operator

x %= 2;
equivalent to x = x % 2

Expontential Assignment Operator

x **= 2;
equivalent to x = x ** 2

Comparison Operators

  • You use these operators to compare the value of a variable with some thing else.
  • The result of an expression, that includes a comparison operator is a boolean, it's true or false

Relational operators

> greater than >= greater than equal to < less than <= less than equal to

Equality operators

Strict equality operator ===

  • Strict equality operator ensures that both operands are of the same type and of the same value.
console.log(1 === 1); //true
console.log(1 === "1"); //false
console.log(1 == true); //false

Loose equality operator ==

  • It will only check if the values are equal.
  • If the types don't match, it will convert the type of what you have on the right side to match what you have on the left side and then checks value
console.log(1 == 1); //true
console.log(1 == "1"); //true
console.log(1 == true); //true

Not Equal Operator

!== - not equal value or not equal type != - not equal value

Ternary Operator or Conditional Operator

  • Assigns a value to a variable based on some condition.
let marks = 80;
let grade = marks > 90 ? "A": "B";
console.log(grade);

Logical Operators

&& (and) || (or) ! (not)

  • Javascript engine evaluates an expression from left to right

Short circuiting

  • The && operator will return false as soon as it gets any false value and will return true if all the values are true.
  • The || operator will return the true as soon as it gets any true value and will return false if all the values are false

Falsy/Falsey

  • Everything without a value is Falsy
  • A Falsy/Falsey value is a value that is considered false when encountered in a Boolean context.
  • Falsy values are
    • undefined
    • null
    • 0, -0
    • false
    • "" (empty string)
    • NaN (not a number)

Truthy

  • Everything with a value is Truthy
  • A truthy value is a value that is considered true when encountered in a Boolean context.
  • Truthy values
    • true
    • , []
    • 40, -42
    • 6.3, -6.3
    • "0"
    • "false"

Logical Opearators with Non-Boolean Values

  • The result of a logical expression is not necessarily a true or false, it depends on the value of the operands you have
  • When JavaScript engine tries to evaluate an expression, it looks at each operand if that operand is not a boolean true or false, it will try to interpret it as truthy or falsey,

&& Operator

  • The && operator will return falsy value as soon as it gets any falsy value and will return the last value if all other values are truthy.
console.log(true && null); //null
console.log(true && undefined); //undefined
console.log(true && 'Ganesh'); //Ganesh
console.log(true && 1); //1
console.log(true && null); //null
console.log(true && undefined); //undefined

||Operator

  • The || operator will return truthy value as soon as it gets any truthy value and will return the last value if all other values are falsy.
console.log('Ganesh' || true); //Ganesh
console.log(1 || true); //1
console.log(false || null); //null
console.log(false || undefined); //undefined

Operator Precedence

https://www.w3schools.com/js/js_precedence.asp

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