1. Number in javascript
javascript numerical types belong to the original type. In addition to the normal values expressed in decimal as we know, we can also use 0x to represent hexadecimal integers, 0b to represent binary integers, and 0O to represent octal integers.
0xa // Corresponding to decimal 10 0b101 //Complied with decimal system 5 0o22 // Corresponding to decimal 18
existjavascript, 0 can be regarded as a divisor, and the return value is infinite. This is very different from other languages. For examplepython0 cannot be used as a divisor.
1/0 // Infinity
Infinity Infinity value
But the result of 0/0 isNaN， NaN It is also a numerical type, which is a special number, indicating that it is not a "numerical" value.
When converting a non-numeric string to a numeric type, the return is also NaN, for example praseInt('a')
Can be usedOr global functionsisNaN Determine whether a value isNaN
(2) //false
('a') // true
('2') //false
The numeric value is a primitive type, and also has corresponding wrapping objects.Number， Number The class provides many methods, including the above mentionedisNaN。
n = new Number(10) () === 10 //true
The value corresponding to object n defined by the wrapper class is exactly equal to the original type value 10.
2. Math object in Javascript
MathThe object isJavascriptThe global object provides many mathematical operation methods
Get the maximum value:
let max = (1,2,3,4) (max) //4
Get the minimum value:
let min = (1,2,3,4) (min) //1
If you are looking for the maximum and minimum values in an array, you can use the extension operator... Decompose the array into multiple parameter values
(...[1,2,3,4]) //4
Round upward:
((2.3)) // 3
Round downward:
((2.8)) // 2
Rounding:
((2.5)) //3 ((2.3)) //2
Randomly generate a floating point number between [0, 1), including 0 but not 1
(())
Randomly generate an integer between 0 and 10
let num = (()*10) (num)
Power:
(2, 10) //1024
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