Chapter 3


JavaScript has only one type of number – 64 bit float point. It's the same as Java's double. Unlike most other programming languages, there is no separate integer type, so 1 and 1.0 are the same value. Creating a number is easy, it can be done just like for any other variable type using the var keyword.

Numbers can be created from a constant value:

// This is a float:
let a = 1.2;

// This is an integer:
let b = 10;

Or, from the value of another variable:

let a = 2;
let b = a;

The precision of integers is accurate up to 15 digits and the maximum number is 17.

let x = 999999999999999;   // x will be 999999999999999
let y = 9999999999999999;  // y will be 10000000000000000

The numeric constants are interpreted as hexadecimal if they are preceded by an 0x.

let z = 0xFF; // 255

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