RegEx Pattern Validations failing on html input

Issue

Issue: I'm trying to achieve the following results for the test cases using a Regex pattern on a input type text html.

Looking to meet the following criteria's:

1. Numeric only - no alpha or special characters allowed

2. No spaces between digits

3. two digits after decimal is allowed

4. Cannot be zero (0)

5. 1st digit of the limit can not be zero (ex:01200)

   testPattern: RegExp = /(?=.*?\d)^\$?(([1-9]\d{0,2}(,\d{3})*)|\d+)?(\.\d{1,2})?$/;

Expected Results:

• 0 //false
• 012 // false
• 0.00 //false
• 0.0 //false
• 0. //false
• 00122 //false
• 0.12 //true
• 0.01 //true
• 1,234.00 // true
• 1.00 //true
• 123,456 //true
• 1.23 // true

TIA

Solution

You could assert not starting with a zero followed by only digits, or only dots, comma's and zero's till the end of the string.

^(?![0,.]*$|0\d*$)\d{1,3}(?:,\d{3})*(?:\.\d{1,2})?$

Explanation

• ^ Start of string
• (?! Negative lookahead
  • [0,.]*$ Match optional zeroes , or . to the end of string
  • | Or
  • 0\d*$ Match 0 and optional digits to the end of string
• ) Close lookahead
• \d{1,3} Match 1-3 digits
• (?:,\d{3})* Optionally repeat matching , and 3 digits
• (?:\.\d{1,2})? Optionally match . and 1-2 digits
• $ End of string

Regex demo

const regex = /^(?![0,.]*$|0\d*$)\d{1,3}(?:,\d{3})*(?:\.\d{1,2})?$/;
[
  "0",
  "012",
  "0.00",
  "0.0",
  "0.",
  "00122",
  "0.12",
  "0.01",
  "1,234.00",
  "1.00",
  "123,456",
  "1.23"
].forEach(s => console.log(`${s} --> ${regex.test(s)}`));

Answered By - The fourth bird