This is an Example to Check Value is a Number using isNaN() in React Native. The function isNaN() is used to check the value of any variable or state is a number or not. In this example we will check input is a number or not.
To Check Value is a Number or Not
1 | isNaN(Pass the Value to check); //It will return true if not a number else false |
It can be used in if condition, as it will return the true or false condition to identify the value, is a number or not. So let’s get started.
To Make a React Native App
Getting started with React Native will help you to know more about the way you can make a React Native project. We are going to use react-native init to make our React Native App.
Assuming that you have node installed, you can use npm to install the react-native-cli command line utility.
Open the terminal and go to the workspace and run
Run the following commands to create a new React Native projectnpm install -g react-native-cli
This will make a project structure with an index file named App.js in your project directory.react-native init ProjectName
Open App.js in any code editor and replace the code with the following code.
App.js
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 | /*This is an example of React Native isNaN() to Check Value Is Number Or Not*/ import React, { Component } from 'react'; import { StyleSheet, View, Button, Alert, TextInput } from 'react-native'; export default class App extends Component { constructor() { super(); this.state = { TextInputValue: '', }; } CheckValueIsNumberOrNot = () => { //Handler called on button click if (isNaN(this.state.TextInputValue)) { //if input is not a number then here Alert.alert('It is not a Number'); } else { //if input is number then here Alert.alert('It is a Number'); } }; render() { return ( <View style={styles.MainContainer}> <TextInput placeholder="Enter text" onChangeText={TextInputValue => this.setState({ TextInputValue: TextInputValue }) } style={styles.TextInputStyle} /> <Button title=" Check Value Is Number Or Not " onPress={this.CheckValueIsNumberOrNot} color="#606070" /> </View> ); } } const styles = StyleSheet.create({ MainContainer: { flex: 1, alignItems: 'center', marginTop: 60, }, TextInputStyle: { textAlign: 'center', height: 50, width: '70%', marginBottom: 10, }, }); |
To Run the React Native App
Open the terminal again and jump into your project using.cd ProjectNamereact-native run-androidreact-native run-ios (macOS only).
This is how you can Check Value is a Number using isNaN() in React Native. If you have any doubt or you want to share something about the topic you can comment below or contact us here. There will be more posts coming soon. Stay tuned!
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