JavaScript basic Functions (methods)

1. Mathematical method: Take random number

Math.random ()

The return value is a random number from 0 to 1, for example:

var n = math.random ();

Then 0=<n<1

Expansion: Random Extraction

var n = parseint (Math.random () * 10);
var arr = [' Bear big ', ' King II ', ' Zhang San ', ' Zhao Si ', ' Liu Wu ', ' Sun Six ', ' money Seven ', ' Li Ba Luyi ', ' Zhou Jiu ', ' Wu 10 '];
Alert (Arr[n]);

Returns an integer from 1 to 10, using the integer as the index value to extract the corresponding name in the ARR array.

2. Get time

var time = Date (); var New Date ();

Get a timestamp in the format: Week-day-month-year-hour-minute-second-time zone.

Based on the time taken, some of the values in the timestamp can be extracted using other methods:

var day = Time.getday ();//Returns the day of the week in English format
var date = Time.getdate ();//Returns a number (1~31), the date of the current month
var month = Time.getmonth () + 1;//Returns a number (0~11), month of the month, JS a bug, the month is starting from 0 number, so assign to the variable +1
var year = Time.getfullyear ();//Returns a four-digit number of years of the year

var hour = time.gethours ();//Returns a number (0~23), the current hour
var minute =time.getminutes ();//Returns a number (0~59), the current minute
var second = Time.getseconds ();//Returns a number (1~60), the current second

3. Other Mathematical methods:

A, abdication to take an integer:

var int = Math.floor (x);

The return value is an integer,

Take only the integer portion of x, no matter how large the number of decimal points are, as with parseint.

Expansion: If you do not know the method of rounding the whole function, you can x+0.5 after the use of mathematical methods Math.floor. The number obtained must be a rounded number.

B, rounding Integer:

var int = Math.ceil (x);

The return value is an integer,

Take only the integer portion of x, if there are decimals after the decimal point, no matter how small the decimal number, the integer +1.

C, take absolute value:

var int = Math.Abs (x);

The return value is a positive number,

Take the absolute value of x.

D, rounding:

var int = Math.Round (x);

The return value is an integer that takes the rounded integer value of x.

E, n power:

var int = Math.pow (x,n);

The return value is a positive number, which is the n power of X.

F, open Square

var int = MATH.SQRT (x);

The return value is a positive number, which is the square root of x.

JavaScript basic Functions (methods)