Alert user if the password field contains spaces at start or end of the string with javascript

Question

Hi,

I have a password field, and if password contains any spaces at start or end, I would like to alert the user. password can be a phrase so spaces in between the string is allowed.

I am sure it can be done through regex, but I don't have much hands on it.

If some one can please help me out.

Thanks, Tanmay

Answer 1

Like this:

if (/^\s|\s$/.test(str)) {
    //Waah waah waah!
}

Explanation:

• The /.../ expression creates a RegExp object.
• The .test() method checks whether the given string matches the regex.

---

• The | expression in the regex matches either whatever is before it or whatever is after it (an or expression)
• The \s expression matches any single whitespace character (such as a space, tab, or newline, or a fancy unicode space)
• The ^ character matches the beginning of the string
• The $ character matches the end of the string

Thus, the regex reads: Match either the beginning of the string followed by whitespace or whitespace followed by the end of the string.

Answer 2

Where password is the string value of your candidiate:

if(password.match(/^\s|\s$/))
{
  // failed
}

In the regex:

• ^ means "start of line"
• \s means "a whitespace character"
• | means OR
• $ means "end of line"

Answer 3

It's easy to write a regular expression to test whether there is whitespace before or after the text; anchor the test with ^ and $.

/^\s|\s$/

But why even bother the user with it? I think it would be better to trim the whitespace automatically.

str.replace(/^\s+|\s+$/g, '');

No muss, no fuss.