import Phone, { phoneNumberFormat, isValidPhoneNumber } from 'react-phone-number-input'

...

state = { phone: '+79991234567' }

...

return (
    <div>
        +7
        <Phone
            format={ phoneNumberFormat.RU }
            value={ this.state.phone }
            onChange={ phone => this.setState({ phone }) }
            className={ classnames('phone', {
                'phone--invalid': !isValidPhoneNumber(this.state.phone, phoneNumberFormat.RU)
            }) } />
    </div>
)

// Outputs "(999) 123-45-67" in the <input/> field.
// `this.state.phone` is plaintext: "+79991234567".

{
    format : PropTypes.oneOfType
    ([
        PropTypes.shape
        ({
            country  : PropTypes.string.isRequired,
            template : PropTypes.string.isRequired
        }),
        PropTypes.shape
        ({
            template : PropTypes.func.isRequired
        })
    ])
    .isRequired,
    value     : PropTypes.string.isRequired,
    onChange  : PropTypes.func.isRequired
}

{
    // +7 | (123) 456-78-90
    RU:
    {
        country  : '7',
        template : '(xxx) xxx-xx-xx'
    },

    // +1 | (123) 456-7890
    US:
    {
        country  : '1',
        template : '(xxx) xxx-xxxx'
    },

    // Supports any custom phone number format logic
    custom:
    {
        // Generates a proper phone number template for the given input digits,
        // where each digit is designated with an "x" symbol.
        //
        // E.g.: "71234567890" -> "+x (xxx) xxx-xx-xx"
        //
        template(digits)
        {
            // Template for "+7 (123) 456-78-90" is:
            return "+x (xxx) xxx-xx-xx"

            // More complex logic can be implemented here
            // for countries with non-trivial phone number formatting rules.
        }
    }
}