Extended String function method_javascript skills

The String extension method has been very busy and has no time to write your own things. But it is not a taste to watch the day without updating your mood. You only have to collect some good stuff from the Internet.
/*** Delete spaces at the beginning and end ***/
String. prototype. Trim = function (){
Return this. replace (/(^ \ s *) | (\ s * $)/g ,"");
}

/*** Count the number of times a specified character appears ***/
String. prototype. Occurs = function (ch ){
// Var re = eval ("/[^" + ch + "]/g ");
// Return this. replace (re, ""). length;
Return this. split (ch). length-1;
}

/*** Check whether the data is composed of digits ***/
String. prototype. isDigit = function (){
Var s = this. Trim ();
Return (s. replace (/\ d/g, ""). length = 0 );
}

/*** Check whether it is composed of digits, letters, and underscores ***/
String. prototype. isAlpha = function (){
Return (this. replace (/\ w/g, ""). length = 0 );
}

/*** Check the number of items ***/
String. prototype. isNumber = function (){
Var s = this. Trim ();
Return (s. search (/^ [+-]? [0-9.] * $/)> = 0 );
}

/*** Number of returned bytes ***/
String. prototype. lenb = function (){
Return this. replace (/[^ \ x00-\ xff]/g, "**"). length;
}

/*** Check whether Chinese characters are contained ***/
String. prototype. isInChinese = function (){
Return (this. length! = This. replace (/[^ \ x00-\ xff]/g, "**"). length );
}

/*** Simple email check ***/
String. prototype. isEmail = function (){
Var strr;
Var mail = this;
Var re =/(\ w + @ \ w + \. \ w + )(\. {0, 1} \ w *)(\. {0, 1} \ w *)/I;
Re.exe c (mail );
If (RegExp. $3! = "" & RegExp. $3! = "." & RegExp. $2! = ".")
Strr = RegExp. $1 + RegExp. $2 + RegExp. $3;
Else
If (RegExp. $2! = "" & RegExp. $2! = ".")
Strr = RegExp. $1 + RegExp. $2;
Else
Strr = RegExp. $1;
Return (strr = mail );
}

/*** Simple date check. The date object is returned successfully ***/
String. prototype. isDate = function (){
Var p;
Var re1 =/(\ d {4}) [year. /-] (\ d {1, 2}) [month. /-] (\ d {1, 2}) [Day]? $ /;
Var re2 =/(\ d {1, 2}) [month. /-] (\ d {1, 2}) [Day. /-] (\ d {2}) [year]? $ /;
Var re3 =/(\ d {1, 2}) [month. /-] (\ d {1, 2}) [Day. /-] (\ d {4}) [year]? $ /;
If (re1.test (this )){
P = re1.exec (this );
Return new Date (p [1], p [2], p [3]);
}
If (re2.test (this )){
P = re2.exec (this );
Return new Date (p [3], p [1], p [2]);
}
If (re3.test (this )){
P = re3.exec (this );
Return new Date (p [3], p [1], p [2]);
}
Return false;
}

/*** Check whether there are any character characters in the list ***/
String. prototype. isInList = function (list ){
Var re = eval ("/[" + list + "]/");
Return re. test (this );
}