Regex only allow whole and decimal point numbers

Question

I want an input field that only receives whole and decimal point numbers greater than 2.5

const [foreignPackageWeight, setForeignPackageWeight] = useState('')

<input type="text" value={foreignPackageWeight}
  onChange={(e) => {
    setForeignPackageWeight(e.target.value.replace(/[^0-9.]/g, ''))
  }}
/>

But my regex allows for numbers like .1 , ..2 , 3...4 , 5..... How do I change my regex to only allow one decimal point?

Answer 1

A possible solution is a form of lookaround known as a positive lookbehind. Lookarounds allow you to ensure a pattern exists (or doesn't exist) without that pattern becoming part of the results.

/[^0-9.]|(?<=\..*)\./g

Match any of:

• [^0-9.] Anything that is not a digit or a period
• (?<=\..*)\. A period so long as another period appeared earlier in the sequence