CODEWITHSUNDEEP
javascriptregex
JDK
JDK

Reputation: 83

first character can't be dash(-) in expression

how to make regular expression when user enter first character is dash(-) it can't allow(user can enter alpha or numeric AS a first character)

but then after 2nd characters onward user can enter alpha,numeric and dash(-)

Upvotes: 1

Views: 2633

Answers (1)

James Donnelly
James Donnelly

Reputation: 128836

A regular expression might be a bit expensive here. You can simply use charAt(0) to grab the first character from your string, then check to see whether it's the "-" character like so:

var myString = ...

if (myString.charAt(0) === "-")
  // Do this if true
else
  // Do this if false

but then after 2nd characters onward user can enter alpha,numeric and dash(-)

If this, however, means that any characters after the first dash character must be alphanumeric or a dash character, you'd need to use the following regular expression:

/^-[a-zA-Z0-9\-]+$/

Like so:

/^-[a-zA-Z0-9\-]+$/.test(myString);

Here's a Regexper visualisation:

Regexper Visualisation

Upvotes: 2

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