Allow only numbers in Input in React

#react

Use value and onChange property of input field to allow only numbers in textbox.
Inside the onChange handle check whether the entered value is valid number or not. Update the state only when entered value is a valid number.

See the below example to do this.

Example 1,

You can use Number and conditionally change state.

import React, {
    Component
} from 'react';

class AllowOnlyNumber extends Component {
    constructor(props) {
        super(props);

        this.state = {
            telephone: ''
        };
        this.onHandleTelephoneChange = this.onHandleTelephoneChange.bind(this);
    }

    onHandleTelephoneChange = e => {
        let telephone = e.target.value;

        if (!Number(telephone)) {
            return;
        }
        this.setState({
            [e.target.name]: telephone
        });
    };

    render() {
        return ( <
            >
            <
            label > Allow only numbers in Input(React): < / label > <
            input type = "tel"
            name = "telephone"
            placeholder = "Telephone Number"
            value = {
                this.state.telephone
            }
            onChange = {
                this.onHandleTelephoneChange
            }
            / > <
            />
        );
    }
}

Example 2,

You can use regex and conditionally change state.

import React, { Component } from 'react';

class AllowOnlyNumber extends Component {
    constructor(props) {
        super(props);
        this.onHandleTelephoneChange = this.onHandleTelephoneChange.bind(this);  
        this.state = {
            telephone: '',
            regexp : /^[0-9\b]+$/
        }   
    }
    
    onHandleTelephoneChange = e => {
        let telephone = e.target.value;

        // if value is not blank, then test the regex
        if (telephone === '' || this.state.regexp.test(telephone)) {
            this.setState({ [e.target.name]: telephone })
        }
    };

    render() {
        return (
            <>
                < label >Allow only numbers in Input (React) : </ label >
                < input
                    type="tel" name="telephone" placeholder="Telephone Number"
                    value={this.state.telephone}
                    onChange={this.onHandleTelephoneChange}
                / >
            </>
        );
    }
}
export default AllowOnlyNumber;