如何将输入限制为1位数字

<input type="number" min="1" max="9">

from flask import Flask, request

app = Flask(__name__)

@app.route('/validate', methods=['POST'])
def validate_input():
    input_value = request.form['input']
    
    if len(input_value) == 1 and input_value.isdigit():
        return '输入有效'
    else:
        return '输入无效'

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

function validateInput(input) {
    var pattern = /^[1-9]$/;
    return pattern.test(input);
}

var userInput = '5';
if (validateInput(userInput)) {
    console.log('输入有效');
} else {
    console.log('输入无效');
}