JavaScript mailbox Verification-Regular validation

First, RegExp1.1 create RegExp Object

New RegExp ("required, Regular expression", "optional, matching pattern g,i,m")

1.2 Methods for RegExp objects

• Test: Retrieves the specified value in the string, returning True or false.

• EXEC: Retrieves the specified value in the string, returns the found value, and no null.

• Complie: Used to change the regular expression, or to delete the matching pattern.

1.2.1 Test ()

var r1 = new RegExp (' World '); Console.log (R1.test (' Hello, world! ')); Trueconsole.log (R1.test (' Hello, world! ')); Falsevar r2 = new RegExp (' World ', ' I '); Case insensitivity Console.log (r2.test (' Hello, world! ')); Truevar R3 = new RegExp (/world/i); Shorthand Console.log (r3.test (' Hello, world! ')); True

1.2.2 Exec ()

var r1 = new RegExp (' World '); Console.log (R1.exec (' Hello, world! ')); [' World ']console.log (r1.exec (' Hello, world! ')); Nullvar r2 = new RegExp (' World ', ' I '); Case insensitivity Console.log (r2.exec (' Hello, world! ')); [' World ']var r3 = new RegExp (/world/i); Shorthand Console.log (r3.exec (' Hello, world! ')); [' world ']var r4 = new RegExp (' O '); Console.log (R4.exec (' Hello, world! ')); [' o ']var r5 = new RegExp (' O ', ' gi '); Console.log (R5.exec (' Hello, world! ')); [' O ']console.log (r5.lastindex); 5 matches the position of the first character of the text, O is 4, and the next position is 5console.log (r5.exec (' Hello, world! ')); [' O '] matches the first o after the call continues to match Console.log (R5.lastindex); 9console.log (R5.exec (' Hello, world! ')); A null match is not returned Nullconsole.log (R5.lastindex); 0 lastindex Reset to 0

1.2.3 Complie ()

var r1 = new RegExp (' World '); Console.log (R1.exec (' Hello, world! ')); [' World ']r1.compile (' o '); Console.log (R1.exec (' Hello, world! ')); [' O ']r1.compile (' m '); Console.log (R1.exec (' Hello, world! ')); Nullvar r2 = new RegExp (' World '); Console.log (R2.test (' Hello, world! ')); Truer2.compile (' Mazey '); Console.log (R2.test (' Hello, world! ')); False

Second, the regular expression

• ^$: Represents the start and end of a matching value.

• +:1+, one or more.

• *:0+, 0 or more.

• ?: 0 /1, 0 or one.

• {1,2}:1

  <=length<=2, length. < li= "" >

• (): Represents a group of expressions.

• []: matching the range of characters, I understand as a block, a lot of blocks placed in a group () inside.

Iii. examples

<form action= "" > Input: <input type= "text"  name= "Mazey"  id= "Mazey"  placeholder= " Please enter the mailbox "><input type=" button " value=" to verify " onclick=" Check (); " ></form><script>function check () {    var reg = new  regexp ("^[a-z0-9]+ ([. _\\-]*[a-z0-9]) *@ ([a-z0-9]+[-a-z0-9]*[a-z0-9]+.) {1,63} [a-z0-9]+$];  //Regular expression     var obj = document.getelementbyid ("Mazey");  //object to validate     if (obj.value ===  "") { //input cannot be empty          alert ("Input cannot be empty!");         return false;    }else if (! Reg.test (Obj.value)) { //Regular validation does not pass, the format is not         alert ("Verification does not pass!");         return false;    }else{         alert ("Pass!") "); &nbsP;       return true;    }}</script> 

JavaScript mailbox Verification-Regular validation

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JavaScript mailbox Verification-Regular validation