How to allow only English letters in input fields?

Question

So, this is my input field:

How can I allow only English letters?

This is the RegEx

Answer 1

You could use /[A-Za-z]/ regular expression and an input event handler which is fired every time the value of the element changes. Something like below:

const regex = /[A-Za-z]/;
function validate(e) {
  const chars = e.target.value.split('');
  const char = chars.pop();
  if (!regex.test(char)) {
    e.target.value = chars.join('');
    console.log(`${char} is not a valid character.`);
  }
}
document.querySelector('#myInput').addEventListener('input', validate);

<label for="myInput">Type some text:</label>
<input id="myInput" type="text" />

Answer 2

You can use the pattern attribute in your input.

    <input pattern = “[A-Za-z]”>

Answer 3

This should do the trick, all characters except ascii 0-127 which are English characters should be excluded, o through 127 also gives you space, +, -, / and punctuation which is useful, if you want only letters then [^A-z] should do the trick, if you need non-space characters then [^A-z\s] should work:

document.getElementById('english').addEventListener('input', function(){
  this.value = this.value.replace(/[^\x00-\x7F]+/ig, '');
});

React Way:

class InputEnglish extends React.Component {
  constructor(){
    super();
    this.state = {value: ''};
    this.onChange = this.onChange.bind(this);
  }
  onChange(e) {
    let val = e.target.value.replace(/[^\x00-\x7F]/ig, '');
    this.setState(state => ({ value: val }));
  }
  render() {
    return (<input 
        value={this.state.value}
        onChange={this.onChange}
    />);
  }
}

https://codepen.io/anon/pen/QVMgrd

Answer 4

I would try this onChange function:

onChange={(e) => {
  let value = e.target.value

  value = value.replace(/[^A-Za-z]/ig, '')

  this.setState({
    value,
  })
}}

See the codepen: https://codepen.io/bozdoz/pen/vzJgQB

The idea is to reverse your regex matcher with ^ and replace all non-A-z characters with ''