Step between 0 and 1 produces floating point rounding errors

[Max-Lovell]

Environment

System:
OS: macOS
Binaries:
Node: v22.16.0
npm: 10.9.2

are you using the new architecture?
No (Expo-managed workflow)

which version of react & react-native are you using?
React: 19.1.0
React Native: 0.81.5
@react-native-community/slider: 5.0.1
Expo SDK: 54.0.17

Description

when using minimumValue of 0, maximumValue of 1, and a step of 0.1, the value returned by onValueChange shows floating-point precision errors. Instead of returning decimal values (e.g. 0.4), it returns e.g. 0.4000000596046448, this can be seen in the value and the markers. Occurs consistently across iOS and Android in the Expo environment.

Reproducible Demo

import React, { useState } from 'react';
import { View, Text } from 'react-native';
import Slider from '@react-native-community/slider';

export default function App() {
  const [value, setValue] = useState(0);

  return (
    <View style={{ flex: 1, justifyContent: 'center', alignItems: 'center' }}>
      <Slider
        style={{ width: 300 }}
        minimumValue={0}
        maximumValue={1}
        step={0.1}
        value={value}
        onValueChange={(val) => setValue(val)}
      />
      <Text>Value: {value}</Text>
    </View>
  );
}

Potential Fix

Round the computed value before emitting it in onValueChange: value = parseFloat(value.toFixed(6));

Workaround

For a temp workaround users can use:
onValueChange={(val) => setValue(Math.round(val * 10) / 10)}

[Max-Lovell]

also this does the trick just fine for a quick fix

renderStepNumber={false}
StepMarker={(marker)=> (
        <Text style={styles.customStepMarker}>
            {Number(marker.index.toPrecision(step?.toString().length))}
        </Text>
)}

provided you have a step prop available - or just replace that with 2 or something