Regex prevents values ​less than or equal to zero and accepts decimal values

Question

Hello I'm building a form in Angular with FormBuilder and i want to put a validation in Validators.pattern() that prevents values ​​less than or equal to zero and that accepts decimal values

How would the regex expression look? Thanks.

Answer 1

Don't. Sure, you could use something like ^([1-9]\d*(\.\d+)?|0\.\d+)$, but you're better off restricting the input in other ways, like <input type="number" id="quantity" name="quantity" min="0"> for example.

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Explanation of the regex

First of all, it's anchored between ^ and $, so the entire input must be matched. Then, there are two options, separated by |:

1. [1-9] a digit between 1 and 9
   \d* followed by any number of digits
   (\.\d+)? optionally followed by a decimal point and at least one digit

2. 0 a zero
   \.\d+ followed by a decimal point and at least one digit

Note that if it starts with a zero, the decimal point and a following digit are mandatory, while if there's any other leading digit, the decimal point and following digits are optional, although if there is a decimal point, there should be at least one digit after that.