We will be covering 2 topics in this chapter

1. The Values
2. Number System

The Values

In javascript we deal with different values to name a few :

• Numbers
• Strings
• Booleans
• Objects
• null
• undefined

Lets talk about number system and how it is represented in Javascript

Number System

• Javascript has only one number type

  • No integer
  • 64 bit Floating point number based on IEEE-754 (a.k.a Double)
  • special Numbers are:
    1. NaN
    2. Infinity
  • Doesnot map well to comon uderstanding of arithmatic i.e 0.1+ 0.2 = 0.30000000000000004. We can verify that having a look o this code snippet

  console.log(0.1 + 0.2 === 0.3); // false
  

  • In javascript, +ve infinity is larger and -ve infinity is smaller than any number except NaN.
    typeof Infinity is always number

Converting to number

lets see the code snippets.

let a = Number("56");
console.log(a, typeof a); // 56 number

let b = Number("56abc");
console.log(b, typeof b); // NaN number

NaN

• Stands for Not a Number which is a numeric value
• it can be produced by the errors shown below

  let a = Number("abc");
  console.log(a); // NaN
  let b = Number(undefined);
  console.log(b); // NaN
  

• NaN is not equal to itself remember this!

  let b = Number(undefined);
  console.log(b); // NaN
  console.log(b === b); // False
  

  so we also cannot find the index off NaN in an array also

  console.log([1, 2, NaN, 3].indexOf(NaN)); // -1
  

  to check wether the number is NaN we can follow this

  let b = Number(undefined);
  console.log(b); // NaN
  console.log(isNaN(b)); // True