用于HTML表单验证的正则表达式开始时没有空格

Question

I have a form field in which I want to allow 1 to 50 letters, numbers, and spaces in it. Just not start with a space and ends with a space. (Or, alternatively, if it starts with a space, it's not counted toward 50.)

I have something like:

^[^s][a-zA-Z0-9_ ]{1,50}[^s]$

But something like "AB" now doesn't pass, because nothing match the {1,50}.

EDIT:

The regex is for the HTML input element pattern field.

Answer 1

Try this

^\b[\w ]{1,50}\b$

Demo

Answer 2

My comment as an answer ;)

^\s*[a-zA-Z0-9_ ]{1,50}\s*$

This regex will allow entry of white space in the beginning and at the end without requiring it as your attempt (kind of) did.

Regards

Edit:

Combine Tims answer with this and you avoid space only :

^\s*\b[\w ]{1,50}$\s*

This forces the string to have a word boundary - ie must contain a word character .

Answer 3

Or with minimal use of regex:

 function myFunction() { var input = document.getElementById('myInput').value.trim(); if (input.length < 1 || input.length > 50) { document.body.innerHTML += "wrong lenth"; return false; } var re = /^[\\w ]+$/; if (re.exec(input) !== null) { document.body.innerHTML += input + " is valid"; return true; } else { document.body.innerHTML += input + " is not valid"; return false; } } 

 <input id="myInput"> <button onclick="myFunction()">Test</button>