JS built-in function Daquan and basic usage method (i)

One, general functions

Alert function : Displays a warning dialog box, including an OK button.

Syntax: alert ("Hello World");

Confirm function : Displays a confirmation dialog box, including OK, Cancel button.

Syntax: Confirm ("OK to remove xxx?"). ");

prompt function : Displays a dialog box with a text box prompting you to wait for user input.

Syntax: Prompt ("Please enter your user name", "show the default value of the text box here");

Two, String functions

connector ' + ': Connect two strings together

Syntax: Var str= ' a ' + ' B ';//Result: STR has a value of AB

substring function : Syntax 1: Intercept starting from the X-character

var str= "This is my test string";
var sub=str.substring (6);//Result: The value of sub is ' s my test string '

Syntax 2: Intercept characters from the X-bit to the Y-bit

var str= "This is my test string";
var sub=str.substring (0,6);//Result: The value of sub is ' this I '

Slice function : intercepts the characters from the X-position to the Y-position of the countdown

Grammar:
var str= ' This is my test string ';
var slc=str.slce (0,-2);//Result: The value of the SLC is the This is my test strin

substr function

Grammar:
var str= ' This is my test string ';
var subs=str.substr (2,6);//Result: The value of subs is ' I '

tolowercase function : Convert to lowercase

Grammar:
var myString = "Hello";
var lcstring = Mystring.tolowercase (); Result: "Hello"

touppercase function : Uppercase

Grammar:
var myString = "Hello";
var ucstring = Mystring.touppercase (); Result: "HELLO"

string comparisonvar astring = "Hello!"; var bstring = new String ("hello!"); if (astring = = "Hello!") {}//Result: true if (astring = = bstring) {}//Result: true if (astring = = = bstring) {}//Result: false (two objects different, although their values are the same)Retrieving Stringsvar myString = "Hello everybody.";//If the retrieval does not return to 1, the retrieved Word returns the start position in the string if (Mystring.indexof ("every") >-1) {}//Result: true   Find replacement string 
           var myString = "I am your father."  var result = Mystring.replace ("is", "AM");//Result: "I am your father."   special character : \b: Back character \ t: Horizontal tab \ n: newline character \v: Vertical tab \f: page break \ r: Carriage return \ ": double quotation mark \ ': single quote \ \: Backslash 
 Three, string transcoding 
 
   converts characters to Unicode encoding  var myString = "Hello"  ; var code = mystring.charcodeat (3); Returns the Unicode encoding for "L"  (integer) var char = String.fromCharCode (66);//Returns a Unicode 66 character  converts a string to a URL-encoded  var myString = "Hello all" ; var code = encodeURI (myString);//Result: "Hello%20all"  var str = decodeURI (code);//Result: " Hello all "  
 corresponding : 
 encodeURIComponent () decodeuricomponent ()  converts a string to base64 encoding /strong> Base64Encode () Base64decode () use ibid.          

JS built-in function Daquan and basic usage method (i)