如何将键盘输入限制为仅限字母

<input type="text" id="inputField" onkeypress="return onlyAlphabets(event)">
<script>
function onlyAlphabets(event) {
  var key = event.keyCode;
  return ((key >= 65 && key <= 90) || (key >= 97 && key <= 122));
}
</script>

from flask import Flask, request, jsonify

app = Flask(__name__)

@app.route('/validate', methods=['POST'])
def validate_input():
    input_text = request.form.get('input')
    if input_text.isalpha():
        return jsonify({'valid': True})
    else:
        return jsonify({'valid': False})

if __name__ == '__main__':
    app.run()

function validateInput(input) {
  var regex = /^[a-zA-Z]+$/;
  return regex.test(input);
}