How do I include negative decimal numbers in this regular expression?

Question

How do I match negative numbers as well by this regular expression? This regex works fine with positive values, but I want it to also allow negative values e.g. -10, -125.5 etc.

^[0-9]\d*(\.\d+)?$ 

Thanks

Answer 1

You should add an optional hyphen at the beginning by adding -? (? is a quantifier meaning one or zero occurrences):

^-?[0-9]\d*(\.\d+)?$ 

I verified it in Rubular with these values:

10.00 -10.00 

and both matched as expected.

let r = new RegExp(/^-?[0-9]\d*(\.\d+)?$/);  //true console.log(r.test('10')); console.log(r.test('10.0')); console.log(r.test('-10')); console.log(r.test('-10.0')); //false console.log(r.test('--10')); console.log(r.test('10-')); console.log(r.test('1-0')); console.log(r.test('10.-')); console.log(r.test('10..0')); console.log(r.test('10.0.1'));