Javascript string object Extension Method

/*  * Append a string to the end of the string *  */  String. Prototype. append = Function  (STR ){  Return   This  . Concat (STR );}  /*  * Delete the characters at the specified index location. If the index is invalid, no characters will be deleted *  */  String. Prototype. deletecharat = Function  (Index ){ If (Index <0 | index> = This  . Length ){  Return   This  . Valueof ();}  Else   If (Index = 0 ){  Return   This . Substring (1, This  . Length );}  Else   If (Index = This . Length-1 ){  Return   This . Substring (0, This . Length-1 );}  Else  {  Return   This . Substring (0, index) + This . Substring (index + 1 );}}  /*  * Delete the string of the specified index range * */  String. Prototype. deletestring = Function  (START, end ){  If (START = End ){  Return   This  . Deletecharat (start );}  Else  {  If (Start> End ){  VaR Temp =Start; Start = End; End = Temp ;}  If (Start <0 ) {Start = 0 ;}  If (End> This . Length-1 ) {End = This . Length-1 ;}  Return  This . Substring (0, start) + This . Substring (end + 1, This  . Length );}}  /*  * Check whether the string ends with substr *  */  String. Prototype. endwith = Function  (Substr ){  If (Substr. length> This  . Length ){  Return  False  ;}  Else  {  Return ( This . Lastindexof (substr) = ( This . Length-substr. Length ))? True : False  ;}}  /*  * You can use = to compare the two strings if they are equal *  */  String. Prototype. Equal =Function  (STR ){  If ( This . Length! = Str. Length ){  Return   False  ;}  Else  {  For ( VaR I = 0; I < This . Length; I ++ ){  If ( This . Charat (I )! = Str. charat (I )){  Return   False  ;}}  Return   True  ;}}  /*  * Compare the two strings to see if they are equal, Case Insensitive *  */  String. Prototype. equalignorecase = Function  (STR ){ VaR Temp1 = This  . Tolowercase ();  VaR Temp2 = Str. tolowercase ();  Return  Temp1.equal (temp2 );}  /*  * Insert the specified string to the end of the specified position. If the index is invalid, it is directly appended to the end of the string *  */  String. Prototype. insert = Function  (Ofset, substr ){  If (Ofset <0 | ofset> =This . Length-1 ){  Return   This  . Append (substr );}  Return   This . Substring (0, ofset + 1) + substr + This . Substring (ofset + 1 );}  /*  * Determine whether a string is a numeric string *  */  String. Prototype. isallnumber = Function (){  For ( VaR I = 0; I < This . Length; I ++ ){  If ( This . Charat (I) <'0' | This . Charat (I)> '9' ){  Return   False  ;}}  Return   True ;}  /*  * Sort strings in reverse order *  */  String. Prototype. Reserve = Function  (){  VaR Temp = "" ;  For ( VaR I = This . Length-1; I> = 0; I -- ) {Temp = Temp. Concat ( This . Charat (I ));}  Return  Temp ;}  /*  * Set the character at the specified position to another character or string. If the index is invalid, the system will directly return the result without any processing *  */  String. Prototype. setcharat = Function  (Index, substr ){  If (Index <0 | index> This . Length-1 ){  Return   This . Valueof ();}  Return   This . Substring (0, index) + substr + This . Substring (index + 1 );}  /*  * Check whether the string starts with substr *  */  String. Prototype. startwith = Function  (Substr ){  If (Substr. length> This  . Length ){ Return   False  ;}  Return ( This . Indexof (substr) = 0 )? True : False  ;}  /*  * Calculate the length. Each Chinese Character occupies two lengths, and each English character occupies one length *  */  String. Prototype. charlength = Function  (){  VaR Temp = 0 ;  For ( VaR I = 0; I < This . Length; I ++ ){  If ( This . Charcodeat (I)> 255 ) {Temp + = 2 ;}  Else  {Temp + = 1 ;}}  Return Temp;} string. Prototype. charlengthreg = Function  (){  Return   This . Replace (/[^ \ x00-\ xFF]/g ,"**" ). Length ;}  /*  * Remove spaces at the beginning and end *  */  String. Prototype. Trim = Function  (){  Return   This . Replace (/(^ \ s *) | (\ s * $)/g ,"");}  /*  * Test whether it is a number *  */  String. Prototype. isnumeric = Function  (){  VaR Tmpfloat = parsefloat ( This  );  If  (Isnan (tmpfloat ))  Return   False  ;  VaR Tmplen = This . Length- Tmpfloat. tostring (). length;  Return Tmpfloat + "0". Repeat (tmplen) = This  ;}  /*  * Test whether it is an integer *  */  String. Prototype. isint = Function  (){  If ( This = "Nan" ) Return   False  ;  Return   This = Parseint ( This  ). Tostring ();}  /*  * Obtain n identical strings *  */  String. Prototype. Repeat = Function  (Num ){  VaR Tmparr = []; For ( VaR I = 0; I <num; I ++) tmparr. Push ( This  );  Return Tmparr. Join ("" );}  /*  * Merge multiple blank spaces into one blank space *  */  String. Prototype. resetblank = Function  (){  Return   This . Replace (/S +/g ,"");}  /*  * Remove blank space on the left *  */  String. Prototype. ltrim = Function  (){  Return   This . Replace (/^ s +/g ,"" );}  /*  * Remove white space on the right *  */  String. Prototype. rtrim = Function (){  Return   This . Replace (/S + $/g ,"" );}  /*  * Remove blank spaces on both sides *  */  String. Prototype. Trim = Function  (){  Return   This . Replace (/(^ s +) | (S + $)/g ,"" );}  /*  * Reserved number * */  String. Prototype. getnum = Function  (){  Return   This . Replace (/[^ d]/g ,"" );}  /*  * Keep letters *  */  String. Prototype. geten = Function  (){  Return   This . Replace (/[^ A-Za-Z]/g ,"");}  /*  * Retain Chinese characters *  */  String. Prototype. getcn = Function  (){  Return   This . Replace (/[^ u4e00-u9fa5uf900-ufa2d]/g ,"" );}  /*  * Get the byte length *  */  String. Prototype. getreallength = Function (){  Return   This . Replace (/[^ x00-xff]/g ,"--" ). Length ;}  /*  * Truncates a string of the specified length from the left *  */  String. Prototype. Left = Function  (N ){  Return   This . Slice (0 , N );}  /*  * Extract a string of the specified length from the right * */  String. Prototype. Right = Function  (N ){  Return   This . Slice ( This . Length- N );}