Introduction to JavaScript Number and Math Objects

1. Number in JavaScript

In javascript , numeric types are primitive types. In addition to the decimal values ​​we know, we can also use 0x to represent hexadecimal integers, 0b to represent binary integers, and 0O to represent octal integers.

0xa //corresponds to decimal 10

0b101 //corresponds to decimal 5

0o22 //corresponds to decimal 18

In javascript , 0 can be used as a divisor and the return value is infinity. This is very different from other languages. For example, 0 cannot be used as a divisor in python .

1/0 // Infinity

Infinity represents infinite value

But the result of 0/0 is NaN . NaN is also a numeric type. It is a special value, which means it is not a "numeric" value.

When a non-numeric string is converted to a numeric type, NaN is also returned, for example, praseInt('a')

You can use Number.isNaN or the global function isNaN to determine whether a value is NaN

Number.isNaN(2) //false
Number.isNaN('a') // true
Number.isNan('2') //false

Numeric value is a primitive type, and there is also a corresponding wrapper object Number . Number class provides many methods, including isNaN mentioned above.

n = new Number(10)
n.valueOf() === 10 //true

The value corresponding to the object n defined by the wrapper class is exactly equal to the original type value 10.

2. Math Object in Javascript

Math object is a global object of Javascript , which provides many mathematical operation methods.

Math.max gets the maximum value:

let max = Math.max(1,2,3,4)
console.log(max) //4

Math.min gets the minimum value:

let min = Math.min(1,2,3,4)
console.log(min) //1

If you are looking for the maximum and minimum values ​​in an array, you can use the spread operator... to decompose the array into multiple parameter values.

Math.max(...[1,2,3,4]) //4

Math.ceil rounds up:

console.log(Math.ceil(2.3)) // 3

Math.floor rounds down:

console.log(Math.floor(2.8)) // 2

Math.round rounds to the nearest integer:

console.log(Math.round(2.5)) //3
console.log(Math.round(2.3)) //2

Math.random randomly generates a floating point number between [0,1), including 0 and excluding 1

console.log(Math.random())

Randomly generate an integer between 0 and 10

let num = Math.ceil(Math.random()*10)
console.log(num)

Math.pow power:

Math.pow(2, 10) //1024

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