The JavaScript Programming Language

There is no difference between float and integer. JS have only number type.

Number is 64-bit floating point value what means ±1.7976931348623157 × 10³⁰⁸ for big numbers and ±5 × 10⁻³²⁴ for small numbers.

Integers can be represented between −9007199254740992 (−2⁵³) and 9007199254740992 (2⁵³)

 

Integer literals

//base 10

0, 15, 100000

 

//base 16 (hexadecimal)

0xff , 0xCAFE911

 

//base 8 (octal) - not standard

065

Never use preceeding zero when defining decimal integer because octal numbers uses that.

Converting decimal into hexadecimal: 010number_DecToHex.js

Converting hexadecimal to decimal: 011number_HexToDec.js

 

 

Floating-point literals

Floating numbers have decimal point.

3.14159

2.34e12 //exponential with small e

2.34E12 //exponential with big E

2.34e-2 //negative exponent

 

//converting number to exponential format: 012number_toExponential.js

var n = 1258;
var exp = n.toExponential();

console.log(typeof exp); //string
console.log(exp); //1.258e+3

 

 

Arithmetic and operators

Basic operators are: + - * / and %

Usage of modulo operator % : 013number_modulo.js

 

Also in calculation Math object can be used

Math.pow(8,2)  //64
Math.round(1.2)  //1
Math.ceil(0.6) //1 round up to an integer
Math.floor(.6) //0 round down to an integer
Math.abs(-5) //5
Math.max(x,y,z) //maximal number
Math.min(x,y,z) //minimal number
Math.random()
Math.PI
Math.E
Math.sqrt(3)
Math.sin(0)
Math.log(8)

 

 

Infinity

Division by zero returns Infinity or -Infinity. Infinity has number type. Example: 014number_division_by_zero.js

Infinity can be defined by: 016number_infinity.js

var pi = Number.POSITIVE_INFINITY;

var ni = Number.NEGATIVE_INFINITY;

var inf = -Infinity;

 

 isFinite() - check if the number is finite: 017number_isFinite.js


 isFinite() returns true if its argument is a number other than NaN, Infinity, or -Infinity.

 

 

 

Underflow

In JS number is zero when it is smaller then ±5 × 10⁻³²⁴ . This is called underflow.

var y = -2e-324;  returns negative zero : 019number_negative_zero.js

 

 

NaN

Nan occurs when we try to perform math operation on non number, for example on string. NaN has number type. There is no -NaN.

NaN cases

y = 0 / 0;

x = parseInt('asas', 10);

z = Math.sqrt(-3);

 

isNaN() - check if the result is NaN: 018number_isNaN.js

 

 

Float point rounding error

 In JS 0.3 - 0.2 returns 0.09999999999999998 , and 0.2 - 0.1 returns 0.1. That's why we can't compare those two results.

Rounding error example: 020number_float_rounding_error.js

 

This error can be corrected by:

var z = 0.5 - 0.4; //0.09999999999999998

z = parseFloat(z.toPrecision(12)); //0.1