I am trying to figure out Regex that will only accept below strings.

• 7 and 8 numbers: '1234567' and '12345678'

• 7 and 8 numbers that start with T: 'T234567' and 'T2345678'

• 7 and 8 numbers that start with D: 'D234567' and 'D2345678'

• 7 and 8 numbers that start with TD: 'TD34567' and 'TD345678'

Regex I have is:

/^(T|[0-9]){1}(D|[0-9]){1}([0-9]){5,6}$/

but it's not passing my unit test for 'D234567' and 'D2345678'

CodePudding user response：

You could write the pattern as:

^(?:\d{7,8}|[TD]\d{6,7}|TD\d{5,6})$

Explanation

• ^ Start of string
• (?: Non capture group for the alternatives
  • \d{7,8} Match 7-8 digits
  • | Or
  • [TD]\d{6,7} Match either T or D and 6-7 digits
  • | Or
  • TD\d{5,6} Match TD and 5-6 digits
• ) Close the non capture group
• $ End of string

Regex demo.

CodePudding user response：

I actually figure it out right after posted this question. Simply added |D after T| so like this.

/^(T|D|[0-9]){1}(D|[0-9]){1}([0-9]){5,6}$/