使用JSP结合JQuery获取信用卡信息时无法获取文本框值的问题

Hey there! Let's break down why you're having trouble grabbing values from your text boxes and fix this up step by step.

First, Fix the Incomplete Alert Statement #

Looking at your code snippet, the alert line is cut off mid-way:

alert($("#cardHolderName").val(...

This will throw a syntax error immediately, which could be blocking your entire script from running properly. Finish the statement to test values correctly:

alert($("#cardHolderName").val());

Ensure the DOM is Fully Loaded Before Accessing Elements #

Your script is placed in the <head> section, which runs before the rest of the page (including your input fields) finishes loading. jQuery can't find elements that don't exist yet! Wrap your code inside $(document).ready() to guarantee the DOM is ready:

$(document).ready(function() {
  function dataValidation() {
    var cHolderName = $("#cardHolderName").val();
    var cCardNumber = $("#creditCardNumber").val();
    var eDate = $("#expirationDate").val();
    
    // Use console.log for clearer debugging (better than alert!)
    console.log("Card Holder Name: " + cHolderName);
    console.log("Credit Card Number: " + cCardNumber);
    console.log("Expiration Date: " + eDate);
  }

  // Make sure your function triggers at the right time, e.g., on a button click
  $("#submitBtn").click(function() {
    dataValidation();
  });
});

Double-Check Your Input Element IDs #

Confirm your HTML inputs have the exact IDs you're referencing in jQuery. A tiny typo (like cardholdername instead of cardHolderName) will make jQuery fail to locate the element. Your inputs should look something like this:

<input type="text" id="cardHolderName" placeholder="Card Holder Name">
<input type="text" id="creditCardNumber" placeholder="1234-5678-9012-3456">
<input type="text" id="expirationDate" placeholder="MM/YY">
<button id="submitBtn">Submit Payment</button>

Prevent Default Form Behavior (If Using a Form) #

If you're wrapping inputs in a <form> tag, the default form submission will refresh the page before your script runs. Add e.preventDefault() to stop this:

$("form").submit(function(e) {
  e.preventDefault(); // Stops page refresh
  dataValidation();
});

Debug with the Browser Console #

Instead of relying on alert(), use console.log() to check values. Open your browser's developer tools (F12) and go to the Console tab—if any value shows up as undefined, that means jQuery couldn't find the corresponding input element (usually due to an ID typo or DOM loading issue).

内容的提问来源于stack exchange，提问作者zari