07-types-number.md

Number

Only one type of number in JavaScript whether it has decimal point or not.

const age = 100;
const money = 1000.50
console.log(typeof age); // number
console.log(typeof money); // number

• typeof is used to find out the 'type' of a variable.

• Various operations: addition, subtraction, multiplication, division can be done with nos.

• Example

  "10" * "10" // 100 (number) - converts the strings to number

The above works with multiplication, division and subtraction and not addition, because the + sign is also used for concatenation.

• Math helper methods:

  • Math.round, Math.floor, Math.ceil, Math.random and many others

      Math.round(2.5); // 3
      Math.floor(2.4); // 2
      Math.ceil(2.4); // 3
      Math.random(); // 0.565262543048269 - random no. between 0 and 1

• Modulo and Power operators:

    const smarties = 20;
    const kids = 3;
    const eachKidGets = Math.floor(smarties/kids); // 6
    const leftSmarties = smarties % kids; // 2 - modulo operation
    
    const x = 2 ** 3; // 8 - power operation using power operator (**)
    // or
    const x = Math.pow(2,3); // 8 - power operation using Math.pow

• Example

  0.1 + 0.2 // 0.30000000000000004

Why? Explanation

So, when working with money, don't store them as dollars and cents. Store all of the money in cents as you won't have to deal with fractions only whole nos. When need to display to user, just convert them back.

• Infinity and Negative Infinity:

typeof Infinity; // number

typeof -Infinity; // number

• Not a Number (NaN):

10 / 'dog' // NaN

typeof NaN // number