useLocalStorageNumber

Description

This hook gets and sets a number in localStorage.

Features synchronization across hooks sharing the same key name.

Usage

import { useLocalStorageNumber } from 'react-use-window-localstorage';

In your function component:

const [value, setValue] = useLocalStorageNumber('pi', 3.14159);

The hook takes a key name and an optional default value argument. The default value will be immediately written to localStorage and returned if no value is present already. Uses null when no default value is provided.

Use value and setValue to read and write the value.

Because localStorage accepts strings only, the value is encoded using JSON.stringify() and decoded using JSON.parse().

Additional Features

The hook provides additional features in its return array, should you be interested:

const [value, setValue, loading, available, reset] = useLocalStorageNumber('pi', 3.14159);

A loading value of true indicates that the value is being loaded from localStorage.
An available value of true indicates that localStorage is supported and available for use.
The reset() function sets the value back to the provided default, or null if none was given.

Signature

useLocalStorageNumber(keyName: string, defaultValue?: number | null) => [number | null, (value: number | null) => void, boolean, () => void, () => void]

Props

Prop	Type	Description
keyName	`string`	Required. Key name to use in localStorage.
defaultValue	`number` \| `null`	Optional. Provide a default `number` value when the key's value is not found in localStorage. Will be immediately written to localStorage if not present. Use `null` for no default.

Return

The hook returns an array containing:

Index	Name	Type	Description
0	value	`number` \| `null`	The `number` value from localStorage, when `loading` is `false`. Will be the default value (or `null` if none provided) while loading is `true`. If `null` when not loading, the key was not found in localStorage.
1	setValue	`(value: number` \| `null) => void`	Sets the value in localStorage. Provide `null` to set it back to the default value. Providing `null` will delete the key from localStorage if the default value is `null`.
2	loading	`boolean`	`true` while the value loads from localStorage, `false` otherwise.
3	available	`boolean`	`true` if localStorage is supported and available for use, `false` otherwise.
4	reset	`() => void`	Reset the value to the default.

Example

import * as React from 'react';
import { useLocalStorageNumber } from 'react-use-window-localstorage';

export function UseLocalStorageNumberExample() {
  const defaultValue = 3.14159;
  const [enteredValue, setEnteredValue] = React.useState('');
  const [value, setValue, loading, available, reset] = useLocalStorageNumber('numValue', defaultValue);
  const [value2, setValue2, loading2] = useLocalStorageNumber('numValue', defaultValue);

  return (
    <div>
      {!loading && (
        <div>
          <div>
            Key "numValue":{' '}
            <input
              type="text"
              value={enteredValue}
              onChange={e => setEnteredValue(e.target.value)}
              onKeyPress={e => e.key === 'Enter' && setValue(parseFloat(enteredValue))}
            />
            <button onClick={() => setValue(parseFloat(enteredValue))}>Set</button>
          </div>
          <div>
            <strong>Stored value:</strong> {value}
          </div>
        </div>
      )}
      <div>
        <button onClick={() => reset()}>Reset "numValue" to default</button>
      </div>
      <hr />
      {!loading2 && <div>Another "numValue" hook (different hook, will synchronize): {value2}</div>}
    </div>
  );
}