JavaScript numbers

A Number in JavaScript consists of values on which we can perform arithmetic operations:

• simple integers
  • (e.g. -2, -1, 0, 1, 2)
• floating point decimals
  • (e.g. 0.36, -25.19111)
• infinity
  • (i.e. Infinity in JavaScript, when dividing a number by 0)
• non-number
  • (i.e. NaN to denote the absence of a number where a number should exist)

Performing arithmetic on a number and a string

One quirk about JavaScript is that it allows us to perform certain operations with different data types. This often yields some amusing results:

const mixedEquation = '10' + 5
// '105'

When we add a number to a string, we get a string!

However, when we subtract (or multiply or divide) a string from a number, we get a number!

const mixedSub = '10' - 5
// 5

const mixedMul = 2 * '8'
// 16

const mixedDiv = 10 / '4'
// 2.5

Performing arithmetic on a number and a Boolean

Now, how about the crazy idea of performing arithmetic with a number and a Boolean (a value that is either true or false)? Well:

• true becomes converted to 1
• false becomes converted to 0

Thus, we end up with this wonderful "new math":

const crazyTrue = 2 + true
// 3

const crazyFalse = 2 + false
// 2

Many more quirks exist but we should take note of these for now to show how crazy JavaScript can get!