How to check if IP Address is correct by using Regular Expressions in JavaScript?

Question

I have a TextBox in my HTML page. User is going to enter IP Address and I wanna check it while the user is inserting the digits and not at the end of all address.

If he wrote 3. = Bad IP, can't start with 3
if he wrote 0.0. = Maybe a start of a good IP
if he wrote 255.256. = Bad

The right address can be between 0.0.0.0 and 255.255.255.255

The big problem is to write the Regular Expression that is going to check if the first digit is 0 or 1 or 2, and after it can be not more than two digits and then "." (dot) and more...

Answer 1

Yeah, it isn't that easy, when using RegExp to check, first split the ip by dot, then check the numbers with a loop, if all number ok, is a valid address otherwise, no.

Here's a demo http://www.freewebs .com/swhtam/ YA/RegExpIPcheck.html go to menu View, source for the complete code.

In the demo, I put up another option to check the ip, cause personally i perfer number check against number, check it out see if you agree with me.

BTW, FYI class A (very large networks) ip address allow first octet from 1-126.



Please note that i put 2 space in the link above to get around the 999 page error, so take the space out to use the link thanks

Answer 2

while you are trying out a service working regionally on the device working the assessments, then use the loopback ip address (127.0.0.a million) as a replace of the ip gained out of your dhcp/assigned. while you're submitting that archives to some form or something.... that doesn't make experience, the service can retrieve the distant ip address, alter your server element if achieveable.

Answer 3

Try this function:









Good luck!