<input type="number"
has always been enfant terrible of HTML inputs. Complaints about this input are numerous.
Number input problems
Inconsistency. Different browsers handle them differently. You can enter only numbers in Chromium based browsers. But you can enter any symbol in Firefox and Safari, though they will show an error popup.
Complexity. Valid numbers are not just digits. Number input allows negative (
-100
) and floating point (0.01
) values, as well as scientific notation (-2.3e4
). Which is helpful sometimes, but not every time.Unexpected behavior. Number input will not report the value it considers invalid. Blank string is reported instead. Also, values which have more significant digits than
step
attribute are considered invalid.
Fortunately, HTML allows us to fix most of these problems. So let's create a better number input. Here is the list of basic features to support.
Numeric input features
Validates user input in all modern browsers consistently.
Sets the decimal input mode for on-screen keyboards.
Can increment and decrement when up or down keys pressed.
Setting input attributes
First thing, we apply native input attributes in order to make it function like we want. I'm going to use pattern attribute to sanitize user's text input.
Available patterns
(?:0|[1-9]\d*)
- Allow only digits,1234567890
[+\-]?(?:0|[1-9]\d*)
- Allow positive and negative integers, e.g.1, -2, +3
[+\-]?(?:0|[1-9]\d*)(?:\.\d+)?
- Allow floating integers, e.g.1.001, -123.9
[+\-]?(?:0|[1-9]\d*)(?:\.\d+)?(?:[eE][+\-]?\d+)?
- Allow scientific notation, e.g.-1.314e12
Here is how our HTML should look like now.
<input
type="text"
pattern="(?:0|[1-9]\d*)"
inputMode="decimal"
autoComplete="off"/>
inputMode="decimal"
sets proper keyboard for touch devices.
autoComplete="off"
is needed to disable annoying browser autocomplete, usually such functionality is needed for name-like inputs.
React component interface
// List of available numeric modes
enum Modes {
natural = 'natural',
integer = 'integer',
floating = 'floating',
scientific = 'scientific',
}
type Value = string;
export type Props = {
/** Set controlled value */
value?: Value;
/** Provide a callback to capture changes */
onChange?: (value?: Value) => void;
/**
* Define a number to increase or decrease input value
* when user clicks arrow keys
*/
step?: number;
/** Set a maximum value available for arrow stepping */
max?: number;
/** Set a minimum value available for arrow stepping */
min?: number;
/** Select a mode of numeric input */
mode?: keyof typeof Modes;
};
export const InputNumeric: FC<Props> = ({
value,
step = 1,
max = Infinity,
min = -Infinity,
onChange = () => {},
mode = Modes.scientific,
}) => {
//...
}
Now we need to manage pattern
attribute according to the mode
setting.
const patternMapping = {
[Modes.natural]: '(?:0|[1-9]\\d*)',
[Modes.integer]: '[+\\-]?(?:0|[1-9]\\d*)',
[Modes.floating]: '[+\\-]?(?:0|[1-9]\\d*)(?:\\.\\d+)?',
[Modes.scientific]: '[+\\-]?(?:0|[1-9]\\d*)(?:\\.\\d+)?(?:[eE][+\\-]?\\d+)?',
};
const pattern = patternMapping[mode];
Handle keystrokes
Here is how to handle arrow key presses.
const handleKeyDown = useCallback(
(event: KeyboardEvent<HTMLInputElement>) => {
const inputValue = (event.target as HTMLInputElement).value;
// handle increment
if (event.key === 'ArrowUp') {
// empty input value has to be normalized to zero
const nextValue = Number(inputValue || 0) + step;
if (nextValue <= max) {
onChange(nextValue.toString());
}
}
// handle decrement
if (event.key === 'ArrowDown') {
const nextValue = Number(inputValue || 0) - step;
if (nextValue >= min) {
onChange(nextValue.toString());
}
}
},
[max, min, onChange, step]
);
User input validation
We are going to inform user about expected number format violations via input border color and option hint below input.
We are going to use Tailwind CSS to create this design and error reporting functionality.
peer
class name is necessary to create a CSS selector for an input error message below. invalid:border-red-600
class name paints border with red color when input is invalid.
invisible
class sets visibility:hidden
for the hint message by default. peer-[:invalid]:visible
class unwraps to the following selector .peer:invalid ~ .peer-\[\:invalid\]\:visible
which makes hint visible when it's preceded by the input.peer
in :invalid
state.
export const InputNumeric: FC = () => {
const id = useId();
return (
<fieldset>
<label htmlFor={id}>
Numeric input
</label>
<input
id={id}
className="peer invalid:border-red-600"
aria-describedby={`${id}-helper-text`}
/>
<div
className="invisible peer-[:invalid]:visible"
id={`${id}-helper-text`}>
Please provide valid decimal number
</div>
</fieldset>
);
}
Here is full Numeric input code:
Happy coding!
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