Java Script Command Cheat Sheet
typeof – Use this to check if item is a string, variable, array, object
console.log( ) – display results in console screen.
Arithmetic Operator:
+ y //addition
– //subtraction
* //multiplication
/ //division
% ; //remainder of division
(x ** y); //x to the power of y
//Increment (++)
console.log(++x); //would be 11
console.log(x++); // you would see 10 first in console then add 1
console.log(x);
//Decrement (–)
console.log(–y); //would be 2
Assignment Operator: (A shorthand for arithmetic)
x = x+5; //Long hand = 15
x += 5; //Short hand = 15
x = x * 3; //Long hand = 30
x *= 3; //Short hand = 30
Comparison Operator
//Relational
console.log(x > 0); //greater than (true)
console.log(x >= 1); //greater than or equal (true)
console.log(x < 1); //less than (false)
console.log(x <=1); //less than or equal (true)
//Equality
console.log(x === 1); // is x equal to value (true)
console.log(x !==1); // is x not equal to value (false)
Equality Operator
//Strict Equality (Type + Value)
console.log(1 === 1); // True
console.log(1 === 1); // True
console.log(‘1’ === 1); // False
// Lose Equality (Value)
console.log(1 == 1); // True
console.log(‘1’ == 1); // True
console.log(true == 1); // True
Logical Operator (Boolean)
//Logical AND (&&)
// Returns TRUE if both operands are TRUE
console.log(true && true); //This one shows TRUE
console.log(false && true); //This one shows FALSE
console.log(true && false); //This one shows FALSE
//Logical or (||)
//Returns TRUE if one of the operands is TRUE. Just takes one TRUE to be TRUE!
let highIncome = false;
let goodCreditScore = true;
let eligibleForLoan = highIncome || goodCreditScore;
console.log(eligibleForLoan); //Answer comes out TRUE
Logical Operator (with NON Boolean) – Truthy or Falsy
false || true //True
false || ‘Mosh’ //”Mosh”
false || 1 //1
What are these Falsy (false) values? Here we go:
- undefined
- null
- 0 (Number zero)
- false (Boolean)
- ‘ ‘ (Empty string)
- Nan (Not a number) (Is a special value in JavaScript that does not produce a valid number.)
If we use any of these Falsy values in a logical expression then they will be treated as Falsy.
Anything that is not Falsy is then Truthy.
This is an example of what we call short-circuiting using || in the console on Chrome.
false || 1 || 2 || 4 || true – The answer is 1. Javascript ignores 2,4, and true!
