Unable to input negative sign in input field

Question

I am new to React and I am trying to have a input field which can take values between -40 and 30. I am using Form.Control from react-bootstrap and below is my code

interface Range{
 min: number,
 max: number
}

const defaultState : types.EqParamRange = {
   Max: 0,
   Min: -1,
};

const [stateRange, setRange] = React.useState<types.Range>(defaultState);

<Form.Group
    key="min"
    className="mb-3"
   >
   <Form.Label>Y-min</Form.Label>
   <Form.Control
        type='number'
        disabled={!enableCustomAxis}
        min={-40}
        max={30}
        step={1}
        value={Range.Min}
        onChange={(event) => {
            const target = event.target as HTMLInputElement
            const value = Number(target.valueAsNumber);
             setCustomYAxisRange( Range => ({
                    ...Range,
                    Min: value
                }));                            
        }}  
        required          
        placeholder='Enter minimum value of Y-coordinate'>
    </Form.Control>
</Form.Group>

On clearing the input field, when I try to input minus sign, it does not allow me to do so. How do I resolve this?

I tried using type='text' and pattern which allows negative numbers but it does not work

Provide more context about what you're trying to achieve (e.g., why do you need to handle negative numbers specifically in this form?). — Kamyar Safari
– Kamyar Safari, Commented Jan 26 at 15:15
I need to allow the user to enter negative values in the input field. When the input field is cleared completely and I try to enter a '-' sign, it does not allow me to do so. Currently I need to enter the number and then insert the minus sign at the beginning of the field. I should be able to input minus sign as the first character in the input field — Nico Robin
– Nico Robin, Commented Jan 27 at 3:58

John Detlefs · Accepted Answer · 2025-01-28 06:20:54Z

It's one of the quirks of controlled inputs in React.

When the user types "-", the code then tries to get the valueAsNumber which returns NaN - not a valid number, and so the input isn't allowed, just as if you tried to enter letters.

The answer is to deal with values entered as if they're strings, run some validation, and then when you have a number, update Range

So handling the event as below allows an empty string, a dash, or a negative number as being valid, and anything else is ignored.

 const handleMinChange = (event) => {
    const inputValue = event.target.value;

    // Allow empty string or a valid number string (including negative numbers)
    if (inputValue === '' || /^-?\d+$/.test(inputValue)) {
      setRange((prevRange) => ({
        ...prevRange,
        Min: inputValue,
      }));
    }
  };

Your form input will still be of type number -- it's just the validation that's treating things as text.

Collectives™ on Stack Overflow

Unable to input negative sign in input field

1 Answer 1

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Your Answer

Sign up or log in

Post as a guest

Related