I'm trying to write javascript that validates a form value of a grid coordinate.
The grid has A to H and 1 to 8, with coordinates written as a letter followed by a number eg. "A1", "H8", "B6", "F3".
Can anyone give me a regex that will rule out anything other than coordinates within that range.
I tried the following:
/^[A-H][1-8]$/ based on my really limited knowledge of regex but that hasn't worked out
Your regexp looks correct, you may want to make it more robust in this way: /^\s*[A-H][1-8]\s*$/
This should match things like "A6" or "B7" even with spaces at the beginning or at the end.
A very useful tool to test your regexps is this: https://regex101.com/
i-flag makes it all case insensitive! But there must be a capital letter!
To be sure your string starts with "A"- "H" followed by "1" - "8" it's correct to say ^[A-H][1-8] but then there may be some more content. So you can write a .* to allow some. To get this content, write it between ( and ) to build a group.
^[A-H][1-8](.*)$ If a line matches, you can get the content behind the range out of $1, the first group. Be sure, that your regex works case sensitive!
If you want to prevent matching lines with another range (like "B4 foo Bar bAz D7 xxx" you need a lookaround:
^[A-H][1-8]((?:(?![A-H][1-6]).)*)$ 
but that hasn't worked out- please edit the question to explain what you're expecting and what you're seeing (with related JS code/examples). That regex does what is described - matching strings that consist of only one letter, A to H, followed by a number, 1 to 8 - so if it "doesn't work" the problem isn't the regex itself.^) with a capital letter in the range from "A" to "H" ([A-H]) followed by a digit in the range from "1" to "8" ([1-8]) and then the string must be end ($)