This is my regex which restricts any characters other than numbers -(minus) and .(dot) Regex is as follows

(?!^-)[^0-9\.]

which allows - (minus) only at the start, But i would like to know If i can allow .(dot) only once and restrict the user to type the next .(dot)

My code

oninput => "this.value = this.value.replace(/(?!^-)[^0-9\.]/g,'')"

CodePudding user response：

You want to allow:

• Optional leading minus (-?)
• At least one digit (\d )
• Optional suffix: a dot, followed by at least one digit (\.\d )

An appropriate regex is:

^-?\d (?:\.\d )?$

CodePudding user response：

As I understand, the user is to be restricted to entering the string representation of an integer or float (possibly negative), and that restrictions are to be imposed on a character-to-character basis. You therefore need a sequence of dynamically-constructed regular expressions that each match a single-character string.

I assume the user enters RETURN to signal that no more characters are to be entered. The user is to be permitted to enter RETURN only when the previous entry was a digit.

1. Define r = /[-\d]/.
2. The first character entered must match r.
3. If the first character entered is '-', set r = /\d/, else (as the first character was a digit) set r = /[\d.]/.
4. If the previous character was a period update r = /\d/ and require the user to enter a character that matches r (i.e, a digit); else the user may press RETURN or enter a character that matches r (which could be /\d/ or /[\d.]/).
5. Repeat step 4 until the user presses RETURN.

Note that, in step 4, once r is set /\d/ it remains at that value until the user presses RETURN.

If a user entry (including RETURN) is rejected it would be helpful to display a message giving the reason for it being rejected.