React Native Form - Check if number has a decimal point issue

I have a basic form within a React Native view - as a basic summary it collects van mileage used in calculations at a later date. The form input uses a numeric keyboard, both fields are required and validated. I'd like to validate the number has been entered and that the user hasn't used a decimal point.

For background - heres a shot of the form:

each field is created using a RN TextInput, both are identical bar the state names - code as follows -

<View style={CheckInStyles.textBlock}>
          <Text style={CheckInStyles.introTxt}>
            3. End Mileage.<Text style={CheckInStyles.errorStyle}> * </Text>
          </Text>
          <Text style={CheckInStyles.introTxtOr}>
            (Please enter mileage upon completing your journey).
          </Text>
        </View>
        <View style={formStyles.textInputBlock}>
          <TextInput
            placeholder="Enter Vehicle END Mileage"
            style={formStyles.textInputText}
            value={this.state.endMileage}
            autoCorrect={false}
            returnKeyType="done"
            keyboardType="numeric"
            onSubmitEditing={Keyboard.dismiss}
            onChangeText={text => this.setState({endMileage: text})}
          />
        </View>

the initial state is numeric - code below:

constructor(props) {
      super(props);

      this.state = {
        startMileage:0,
        endMileage:0,
      }
  } 

on validation I have the following code -

    if (this.state.startMileage && this.state.endMileage && this.state.tripReason && Number.isInteger(this.state.startMileage) && Number.isInteger(this.state.endMileage)) {
        
        return true
        
       }
       else {
        return false;
       }

The part I need help understanding is the number / decimal point check - i'm using

Number.isInteger()  

If I use a direct number ie:

Number.isInteger(3.3)

the result is false - as expected

Number.isInteger(3)

the result is true as expected

If however I use the state numeric value -

Number.isInteger(this.state.endMileage)) 

regardless of whether the value is a whole or contains a decimal point - the results is always false.

Is this because the state input is using a text input and the value is converted to a string? Can anyone advise a solution / explanation? Thanks.

"Is this because the state input is using a text input?" Yes, it is exactly this.

Number.isInteger(value) will always return false if the value is not a number.

You could look into Number.parseFloat, and possibly pass keyboardType="number-pad" rather than numeric.