Perfect solution to validate a password

Question

I took an online JavaScript test where the 3rd problem was as follows:

Complete the checkPassword function, which should check if the password parameter adheres to the following rules:

Must be longer than 6 characters.
Allowed characters are lower or uppercase Latin alphabetic characters (a-z), numbers (0-9), and special characters +, $, #, \, / only.
Must not have 3 or more consecutive numbers (e.g. "pass12p" is fine, but "pass125p" is not, because it contains "125")

>

My solution was as follows:

function checkPassword(password) {
  return /^[a-zA-Z0-9\+\$\\\/#]{6,}$/.test(password) && !/[0-9]{3,}/.test(password);
}

This solution gave me the correct outputs for the given inputs.

But the ultimate test result told that the solution is just 75% correct sadly.

I think the perfect answer is expected to be a solution just with a single regular expression. Is there anyone who can give me a single regular expression that gives the same result? I am not so good at regular expression so please advise.

I appreciate your help in advance.

Welcome to SO! Please do search the site before asking a question - this exact one has been already answered. — georg, Feb 14 '15 at 17:23

Avinash Raj · Accepted Answer · 2015-02-14T17:00:05.180

3

Just use a negative lookahead at the start.

^(?!.*?\d{3})[a-zA-Z0-9\+\$\\\/#]{6,}$

(?!.*?\d{3}) at the start asserts that the match won't contain atleast three consecutive digits. Then the regex engine tries to match the pattern [a-zA-Z0-9\+\$\\\/#] against the input string 6 or more times only if this condition is satisfied.

DEMO

edited Feb 14 '15 at 17:00

answered Feb 14 '15 at 16:54

Avinash Raj

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The full lookahead syntax is: x(?!y) - where you mean x can be an empty value? – Microtribute Feb 14 '15 at 17:06
Because you're new to StackOverflow, i suggest you to read [this](http://stackoverflow.com/help/accepted-answer). – Avinash Raj Feb 14 '15 at 17:07
The full lookahead syntax is: x(?!y) - where you mean x can be an empty value? – Microtribute Feb 14 '15 at 17:09
`x(?!y)` matches all the `x` which isn't followed by a character `y` . Likewise `^(?!.*?\d{3})` checks for the whole line where min 3 consecutive digits present or not. And this `(?!.*?\d{3})` assertion won't match even a single character. It's just an assertion whether the match is possible or not. – Avinash Raj Feb 14 '15 at 17:11
How do I mark your answer accepted? – Microtribute Feb 14 '15 at 17:11
^(?!.*?\d{3}) is considered to have an empty x value, isn't it? – Microtribute Feb 14 '15 at 17:12
yep, right. Just click the tick mark present below to the down arrow. – Avinash Raj Feb 14 '15 at 17:15

score 0 · Answer 2 · answered Feb 14 '15 at 17:03

0

 ^(?=.*\d)(?=.*[a-z])(?=.*[A-Z])[a-zA-Z\d]{6,}$

For consecutive number check

    public boolean isValid(final String userName,final String password) { 
    for(int i=0;(i+2)<userName.length();i++) if(password.indexof(userName.substring(i,i+2))!=-1) return false; return true; 
}

answered Feb 14 '15 at 17:03

Fahim

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Java : Javascript = Ham : Hamster – georg Feb 14 '15 at 17:22

Perfect solution to validate a password

2 Answers2