JavaScript functions and JS package features at a glance

Function four elements: return type, function name, argument list, function body

function type

Simple functions

1 function Ceshi () {2    alert ("This is the test"); 3 }4 Ceshi ();

Parametric functions

1 function Ceshi (A, b) {2    alert (a+b); 3 }4 Ceshi (2,3);

There is a default function (JS is not supported)

1 function Ceshi (a,b=5) {2    alert (a+b); 3 }4 Ceshi (2);

Functions that have return values

1 function Ceshi (A, b) {2    return a+b; 3 }4var c=ceshi (2,3); 5 alert (c);

Knowledge Points:

Naming conventions for variables: captions begin, not Chuxian special symbols, usually lowercase

Naming conventions for functions: first-Letter Lowercase hump method, Chifanle

Encapsulates a function function: Encapsulates a bubbling sort code

1 function Paixu (arr) {2   //Bubble Sort Code3   var arr=new Array (45,56,23,78,89,99,36,77,100);4   var zj=0; Intermediate Variables5for (i=1;i<arr. length;i++) {//Used to control rounds6 For (J=0;j<arr.length-i;j++) {//To control the number of times7           if (arr[j]<arr[j+1]) {8 ZJ=arr[j];9               Arr[j]=arr[j+1];Ten               Arr[j+1]=zj; One           } A       } -   } -   alert (arr[0]); the } - return arr; - var a=newArray (1,4,3,2,6,8); - a=paixu (a); + alert (a[0]);

JavaScript package Features at a glance:

Mathematical functions
1alert (Math.random ());                  Returns a random number between 0-1 and 2alert (math.random () *10);               Returns a random number between 1-10 and 3 alert (parseint (Math.random () *10));     Returns a random integer between 1-10
4 Alert (Math.ceil (1.2));                 To take the whole  
5 Alert (Math.floor (1.2));                Take down the whole

//Get Time
1 var d=new Date ();2 alert (d); Get current Time3 alert (D.gettime ()); Get time stamp4 alert (D.getfullyear ()); Get year5 alert (D.getmonth () +1); Get Month6 alert (D.getdate ()); Get Day7 alert (d.gethours ()); Get hours8 alert (D.getminutes ()); Get minutes9 alert (D.getseconds ()); Get secondsTen alert (D.getday ()); Get the day of the week OneAlert (D.getmilliseconds ()); Get milliseconds

Mathematical functions (called with math):
ABS (x) The absolute value of the return number.
Ceil (x) is rounded on the logarithm.
Floor (x) is rounded down with a logarithmic.
Round (x) rounds the number to the nearest integer.
Max (x, y) returns the highest value in X and Y.
Min (x, y) returns the lowest value in X and Y.
The POW (x, y) returns the y power of X.
SQRT (x) returns the square root of the number.
Random () returns an arbitrary number between 0 and 1. ****

String functions (called with variables):

IndexOf
Returns the index (from left to right) of the first occurrence of a substring in a string. If there is no match, returns-1.
var index1 = A.indexof ("L");
INDEX1 = 2

CharAt
Returns the character at the specified position.
var Get_char = A.charat (0);
Get_char = "H"

LastIndexOf
Returns the index (right-to-left search) at the last occurrence of a substring in a string, or 1 if there are no matches.
var index1 = lastIndexOf (' l ');
INDEX1 = 3

Match
Checks if a string matches the contents of a regular expression, and returns null if there is a match.
var re = new RegExp (/^\w+$/);
var is_alpha1 = A.match (re);
IS_ALPHA1 = "Hello"
var is_alpha2 = B.match (re);
IS_ALPHA2 = null

Substring
Returns a substring of a string in which the incoming parameter is the starting and ending position.

var sub_string2 = a.substring (1,4);
Sub_string2 = "ell"

SUBSTR ********
Returns a substring of a string in which the incoming parameter is the starting position and length
var sub_string1 = a.substr (1);
Sub_string1 = "Ello"
var sub_string2 = a.substr (1,4);
Sub_string2 = "Ello"

Replace *******
Replace String, the first argument represents the replaced string, the second argument represents the replacement string
A.replace ("he", "AA")

Search
Performs a regular expression matching lookup. If the lookup succeeds, returns the matching index value in the string. otherwise returns-1.
var index1 = A.search (re);
index1 = 0
var index2 = B.search (re);
Index2 =-1

Split ******
A string is made into a string array by dividing the string into substrings.
var arr1 = A.split ("");
ARR1 = [H,e,l,l,o]

Length property *******
Returns the length of a string, which refers to the number of characters it contains.

toLowerCase
Turns the entire string into lowercase letters.
var lower_string = A.tolowercase ();
lower_string = "Hello"

toUpperCase
Turns the entire string into uppercase.
var upper_string = A.touppercase ();
upper_string = "HELLO"

JavaScript functions and JS package features at a glance