How to validate TextInput values in react native?

You can use a regex to check if the mail entered is valid.

Regex function

validateEmail = (email) => {  var re = /^(([^<>()\[\]\\.,;:\s@"]+(\.[^<>()\[\]\\.,;:\s@"]+)*)|(".+"))@((\[[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}])|(([a-zA-Z\-0-9]+\.)+[a-zA-Z]{2,}))$/;    return re.test(email);};

Submit text input function

onSubmit = () => {if (!this.validateEmail(this.state.text_input_email)) {  // not a valid email} else {  // valid email}

You can validate your input value using onBlur event on TextInputYou can apply your regex or check conditions on this event.

Like this:

<TextInput      onBlur= () => {        //Conditions or Regex      }/>

In your case,Regex function:

validateEmail = (email) => {var re = /^(([^<>()\[\]\\.,;:\s@"]+(\.[^<>()\[\]\\.,;:\s@"]+)*)|(".+"))@((\[[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}])|(([a-zA-Z\-0-9]+\.)+[a-zA-Z]{2,}))$/;return re.test(email);};

Text Input Code:

<TextInput  onBlur= () => {    if (!this.validateEmail(this.state.text_input_email)) {       // not a valid email    } else {       // valid email    }  }/>