use-validated-state

Validate state and get last valid value
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Package
@mantine/hooks

Usage

use-validated-state validates state with a given rule each time state is set. It returns an object with current validation state, last valid value and current value:

const [{ lastValidValue, value, valid }, setValue] = useValidatedState(
  'valid',
  (value) => value === 'valid'
);


lastValidValue; // -> valid
value; // -> valid
valid; // -> true


setValue('invalid');


lastValidValue; // -> valid
value; // -> invalid
valid; // -> false

Example

Current value: [empty string]
Last valid value: [empty string]
import { TextInput, Text } from '@mantine/core';
import { useValidatedState } from '@mantine/hooks';


function Demo() {
  const [{ value, lastValidValue, valid }, setEmail] = useValidatedState(
    '',
    (val) => /^\S+@\S+$/.test(val),
    true
  );


  return (
    <div style={{ maxWidth: 320, margin: 'auto' }}>
      <TextInput
        value={value}
        onChange={(event) => setEmail(event.currentTarget.value)}
        withAsterisk
        error={!valid}
        placeholder="email@example.com"
        label="Your email"
      />


      <Text size="sm" mt="md">
        <Text inherit color="dimmed" component="span">
          Current value:
        </Text>{' '}
        {value || '[empty string]'}
      </Text>
      <Text size="sm">
        <Text inherit color="dimmed" component="span">
          Last valid value:
        </Text>{' '}
        {lastValidValue || '[empty string]'}
      </Text>
    </div>
  );
}

Definition

function useValidatedState<T>(
  initialValue: T,
  validation: (value: T) => boolean,
  initialValidationState?: boolean
): [
  {
    value: T;
    lastValidValue: T;
    valid: boolean;
  },
  (val: T) => void
];
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