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Implementation and technical analysis of the verification code generated by js

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Implementation and technical analysis of the verification code generated by js

I will share with you a piece of code for generating and verifying the verification code in js.

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<! DOCTYPE html PUBLIC "-// W3C // dtd xhtml 1.0 Transitional // EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<Html xmlns = "http://www.w3.org/1999/xhtml">

<Head>

<Title> JS verification code generation </title>

<Style type = "text/css">

. Code {

Background-image: url(code.jpg );

Font-family: Arial;

Font-style: italic;

Color: Red;

Border: 0;

Padding: 2px 3px;

Letter-spacing: 3px;

Font-weight: bolder;

}

. Unchanged {

Border: 0;

}

</Style>

<Script language = "javascript" type = "text/javascript">

Var code; // define the verification code globally

Function createCode (){

Code = "";

Var codeLength = 6; // The length of the Verification Code

Var checkCode = document. getElementById ("checkCode ");

Var selectChar = new Array (0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 'A', 'B', 'C ', 'D', 'E', 'F', 'G', 'h', 'I', 'J', 'k', 'l', 'M ', 'N', 'O', 'P', 'Q', 'R', 's', 't', 'U', 'V', 'w ', 'X', 'y', 'z'); // All characters of the Verification Code composed of candidates.

For (var I = 0; I <codeLength; I ++ ){

Var charIndex = Math. floor (Math. random () * 36 );

Code + = selectChar [charIndex];

}

// Alert (code );

If (checkCode ){

CheckCode. className = "code ";

CheckCode. value = code;

}

}

Function validate (){

Var inputCode = document. getElementById ("input1"). value;

If (inputCode. length <= 0 ){

Alert ("Enter the verification code! ");

} Else if (inputCode! = Code ){

Alert ("Incorrect verification code! ");

CreateCode (); // refresh the verification code

} Else {

Alert ("^-^ OK ");

}

}

</Script>

</Head>

<Body onload = "createCode ()">

<Form action = "#">

<Input type = "text" id = "input1"/> <input type = "text" onclick = "createCode () "readonly =" readonly "id =" checkCode "class =" unchanged "style =" width: 80px "/> <br/>

<Input id = "Button1" onclick = "validate ();" type = "button" value = "OK"/>

</Form>

</Body>

</Html>

As we all know, JavaScript is a client, is it meaningful to make all the verification on the client? Is the verification code generated from the server safe? Is the verification code generated by the front-end secure?

The verification code is dynamic, but it must be identified by the client and the correct value should be returned for normal verification. This is a process problem. if Javascript is used, it is verified on the client. It is basically the same !!! It is best to generate a server, verify the client, confirm the server, and browse normally. Such a process is foolproof.

This article is an English version of an article which is originally in the Chinese language on aliyun.com and is provided for information purposes only. This website makes no representation or warranty of any kind, either expressed or implied, as to the accuracy, completeness ownership or reliability of the article or any translations thereof. If you have any concerns or complaints relating to the article, please send an email, providing a detailed description of the concern or complaint, to info-contact@alibabacloud.com. A staff member will contact you within 5 working days. Once verified, infringing content will be removed immediately.

Related Keywords:
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