JS Date Math Number

Date Object

The Date object, unlike the string object, defines a string that, in fact, is a string object that can call properties and methods directly.

The use of the Date object must be created with the new keyword, otherwise the properties and methods of the date object cannot be called.

Create Date methods of the object

(1 ) Create current ( now) An instance of a Date object with no parameters

　　　　　　　　var timer = new Date ();

　　　　(2) Create a Date object instance of the specified timestamp, the parameter is a timestamp

Timestamp: Refers to the number of millisecond values (1 seconds =1000 milliseconds) that have elapsed in the past, 0 seconds from January 1, 1970 0:0.

var timer = new Date (10000); Time is January 1, 1970 0:0 10 seconds

(3 Specifies a date-time information for a string that is a datetime string

var timer = new Date ("2015/5/25 10:00:00");

　　　　(4 ) to specify multiple numeric parameters

var timer = new Date (2015+100,4,25,10,20,0);

The order is: year, month, day, time, minute, second, year, month, day is necessary.

getFullYear (): Gets the four-bit year.

GetMonth (): Gets the month, with a value of 0-11.

GetDate (): Gets the number, takes the value 1-31

GetHours (): Gets the number of hours.

Getminutes (): Number of minutes

Getseconds (): Number of seconds

Getmilliseconds () MS

GetDay () Week

GetTime () millisecond value, the millisecond value from January 1, 1970 to the present

Math Mathematical Object

The Math object is a static object, in other words: When you use the Math object, you do not need to create an instance.

Math.PI: Pi.

Math.Abs (): absolute value. Example: Math.Abs (-9) = 9

Math.ceil (): Rounding up (integers plus 1, decimals removed). Example: Math.ceil (10.2) = 11

Math.floor (): Rounding down (directly minus decimals). Example: Math.floor (9.888) = 9

Math.Round (): Rounded.    such as: Math.Round (4.5) = 5; Math.Round (4.1) = 4

Math.pow (x, y): X is the y-square. Example: Math.pow (2,3) = 8

MATH.SQRT (): To find the square root. Example: math.sqrt (121) = 11

Math.random (): Returns a random decimal number between 0 and 1. Example: math.random () = 0.12204467732259783

A random integer between 0-10, a random integer between 10-20 and a random integer between 20 and 30; Find a random integer between 7 and 91

　　

　　

Number Numeric Object

A numeric variable, which is a numeric object (number Object).

ToFixed ()

Function: Converts a numeric value to a string and rounds it, preserving a decimal number of the specified digits.

Syntax: numobj.tofixed (n)

Parameter: N is the number of decimal digits to keep.

Example:

var a = 123.9878;

A = a.tofixed (2); A = "123.99"

JS Date Math Number