Instructions for validating an input field with yup to ensure it does not begin with '-', '+', or '_'

Is there a way to validate user input using YUP and restrict values that begin with '-', '+', or '_'?

Thank you for your help!

name: Yup.string()
    .required()
    .min(5, 'Too short')
    .matches(/^[aA-zZ\s]+$/, "Only alphabets are allowed for this field ")
    .matches()//code for checking wheather it starts with '+','-','_' if it starts I need to show an error

If you could provide the regex pattern for the following criteria:

  1. Minimum length of 5 characters
  2. No special characters allowed
  3. Cannot start with '-', '_', or '+'
javascriptregexnext.jsyup

Answer №1

Ensure that your desired inputs are matching the regex /^[_\-\+]{1}.*/:

const startsWithSpecialChars = /^[_\-\+]{1}.*/;

console.log('"hello" ==> ', !!'hello'.match(startsWithSpecialChars));
console.log('"hel+lo" ==> ', !!'hel+lo'.match(startsWithSpecialChars));
console.log('"_hello" ==> ', !!'_hello'.match(startsWithSpecialChars));
console.log('"-hello" ==> ', !!'-hello'.match(startsWithSpecialChars));
console.log('"+hello" ==> ', !!'+hello'.match(startsWithSpecialChars));

Here's a breakdown of the regex:

  • ^ signifies the start of the string
  • [_\-\+]{1} denotes exactly one character of _, -, or + (hyphen and plus sign are escaped)
  • .* indicates any number of characters following underscore, hyphen, or plus symbol

Noteworthy is that "hello" and "hel+lo" do not match, while "_hello", "-hello", and "+hello" do.

It's worth mentioning that the second condition (

.matches(/^[aA-zZ\s]+$/, "Only alphabets are allowed for this field ")
) may not function as intended; reconsider its implementation.

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