更正错误后无法提交表单

document.getElementById('myForm').addEventListener('submit', function(event) {
    if (!validateForm()) {
        event.preventDefault();
    }
});

function validateForm() {
    var input = document.getElementById('userInput').value;
    if (input === '') {
        alert('输入不能为空');
        return false;
    }
    return true;
}

from flask import Flask, request, jsonify

app = Flask(__name__)

@app.route('/submit', methods=['POST'])
def submit():
    data = request.get_json()
    if not data['username']:
        return jsonify({'error': '用户名不能为空'}), 400
    return jsonify({'success': True}), 200

import logging

logging.basicConfig(level=logging.ERROR)

@app.route('/submit', methods=['POST'])
def submit():
    try:
        data = request.get_json()
        # 处理数据
        return jsonify({'success': True}), 200
    except Exception as e:
        logging.error(f'处理表单数据时出错: {e}')
        return jsonify({'error': '服务器内部错误'}), 500