Methods for js-objects

String Object method
var str = ' Hello ';
Console.log (str.length); 5
Console.log (Str[0]); H
STR itself holds string type data, but converts the object to a pseudo object when used
So you can reference the properties of a string object
Pseudo-object: For the basic type of data, when reading, JS will convert the data into the corresponding pseudo-object, and then read the pseudo-object (i.e.
Read out is the object type, so there are corresponding attributes).

Split is used to split a string into a string array
var str = ' Hello,world '
var result = Str.split (' l ');
Console.log (result);

var str = ' 123012301230456789 '
var result = Str.split (' 123 ');
Console.log (result);
["", "0", "0", "0456789"]

var str = ' 123012301230456789 '
var result = Str.split (' a ');
Console.log (result);
["123012301230456789"]

var str = ' 123012301230456789 '
var result = Str.split (");
Console.log (result);
["1", "2", "3", "0", "1", "2", "3", "0", "1", "2",
"3", "0", "4", "5", "6", "7", "8", "9"]

charCodeAt () returns the Unicode encoding of the character at the specified position, and the result must be a number
var str = ' Hello ';
Console.log (Str.charcodeat (1)); 101

The concat () connection string, which converts all its arguments to a string,
It then connects sequentially to the end of the string stringobject and returns the concatenated string
Same array usage Note: + also has the same function
var str = ' Hello ';
var result = Str.concat (' js ', ' haha ')
Console.log (result);
Hellojshaha
Console.log (str);
Hello

IndexOf () returns the position of the first occurrence of a string fragment in a string, from left to right
var str = ' Hello ';
var result = Str.indexof (' el ');
Console.log (result); 1

var str = ' Hello '; Search from left to right, search for the first L's Corner label
var result = Str.indexof (' l ');
Console.log (result); 2

var str = ' Hello '; String not retrieved, return value is-1
var result = Str.indexof (' lll ');
Console.log (result); -1

var str = ' Hello, world ';
var result = Str.indexof (' l ', 6);
6 The representative starts with the first search
Console.log (result); 10

LastIndexOf () Search from right to left

Replace () replaces the character in a string, replacing only the first satisfied character,
If you want to replace all, you need to use regular expressions
var str = ' Hello, world ';
var result = str.replace (' l ', 0);
L: The character you want to replace 0: what to replace
Console.log (result);
He0lo,world
Console.log (str);
Hello,world

Slice () intercept fragment, same as array
var str = ' Hello, world ';
var result = Str.slice (3,-1);
Console.log (result); Lo, Worl

toUpperCase () Convert uppercase
var str = ' helLo, world ';
Console.log (str);
HelLo, World
var result = Str.touppercase ();
Console.log (result);
HELLO, World
Console.log (str);
HelLo, World

toLowerCase () Convert lowercase

The method of the Number object (Everything is objects, objects are used)
ToString () Any object has (JS bottom)
var a = ' 123 ';
var b = 100;
var result = a + B;
1. Convert A and B to the corresponding pseudo-object for reading
2, because the + symbol is a string connection operator, this time will call two pseudo-object ToString ()
method to stitch the return values of two methods together
Console.log (result); 123100

ValueOf () Converts a string to a number, which is owned by any object (JS bottom)
var a = ' 123 ';
var b = 100;
var result = A-B;
-only add and subtract operations
Console.log (result); 23

ToFixed () specifies that several decimals are kept, rounded, and the result is a string
var num = 1.23456;
Console.log (num.tofixed (2)); 1.23
Console.log ((1.2345). toFixed (2)); 1.23 Method Two

Toexexponential () Converts the result to an exponential count method with the result of a string
var num = 123456.789;
Console.log (Num.toexponential ()); 1.23456789e+5

Toprecision specify the number of digits of the exponential count method
var num = 123456.789;
Console.log (Num.toprecision (2)); 1.2e+5

Math Object
Property:
PI: Return pi
Console.log (Math.PI); 3.141592653589793

Method:
ABS (x) absolute value of the return number
Console.log (Math.Abs (10)); 10
Console.log (Math.Abs (-10)); 10

Min (x, y) max (x, y) is better in low-version ie than if
Console.log (Math.min (10,12)); 10
Console.log (Math.max (10,12)); 12

Ceil (x) rounding on a logarithmic
Console.log (Math.ceil (10.01)); 11
Console.log (Math.ceil (10.00)); 10

Floor (x) logarithm is rounded down
Console.log (Math.floor (10.99)); 10
Console.log (Math.floor (10.00)); 10
//
Round (x) rounding
Console.log (Math.Round (10.4)); 10
Console.log (Math.Round (10.6)); 11

Random (x) generates random decimals between 0-1
var num = Math.random ();
Console.log (num); 0.9598256822289126

Generate random numbers between 0-20
Randomly generate 0-1 decimals, multiply by 21, and then go down to rounding
Console.log (Math.floor (Math.random () *20));
Generate random numbers between 1-20
Randomly generate 0-1 decimals, multiply by 20, and then go up to the rounding

Date objects represent dates or times
var mydate = new Date (); Create a date way, no literal way
Console.log (mydate); Wed Oct 10:54:59 gmt+0800 (China Standard Time)

Method:
Date () Returns the day and time
Console.log (Date ()); Wed Oct 10:56:44 gmt+0800 (China Standard Time)

GetDate () returns the number of
var mydate = new Date ();
Console.log (Mydate.getdate ());
//
GetMonth () returns months 0 to month
var mydate = new Date ();
Console.log (Mydate.getmonth ());
//
getFullYear () return year
var mydate = new Date ();
Console.log (Mydate.getfullyear ());
//
GetDay () Returns the day of the week 0 for Sunday
var mydate = new Date ();
Console.log (Mydate.getday ());

GetHours () returns the number of hours getminutes/getseconds/getmilliseconds get milliseconds
Generate timestamps, get unique
(The low version browser can only be accurate to 10 milliseconds or 30 milliseconds)
var mydate = new Date ();
Console.log (Mydate.gethours ());

getTimezoneOffset () Get the time difference between local and standard time (minutes)
var mydate = new Date ();
Console.log (Mydate.gettimezoneoffset ());

getUTCHours () Get the hour of standard Time
var mydate = new Date ();
Console.log (Mydate.getutchours ());

Sethours () set several
var mydate = new Date ();
Mydate.sethours (10); Set the current time to 10 points
Console.log (Mydate.getutchours ());

ToString converts the current date to a string in the format English
var mydate = new Date ();
Console.log (Mydate.tostring ());

toLocaleString () show current date according to local custom
var mydate = new Date ();
Console.log (Mydate.tolocalestring ());

toTimeString () Get time only
var mydate = new Date ();
Console.log (Mydate.totimestring ());

toLocaleTimeString () according to local habits
var mydate = new Date ();
Console.log (Mydate.tolocaletimestring ());

Methods for js-objects