How to use JavaScript to check if a request has been submitted repeatedly

When modern websites process user requests, they sometimes need to check whether the user request has been submitted repeatedly. Repeated submissions may cause data anomalies or system crashes. JavaScript is a very important part of front-end development and can help us check whether requests are submitted repeatedly. In this article, we will discuss how to use JavaScript to check if a request is submitted twice.

Part 1: What is duplicate submission?

In the field of web development, there are two common scenarios for repeated submissions: first, after submitting the form, the user may accidentally or maliciously submit the same form data repeatedly; second, after the user clicks a button or link At this time, network delays or other problems may occur, causing users to mistakenly think that the submission was unsuccessful and then submit again. These will lead to duplicate submissions.

Duplicate submissions may have an impact on the application, such as causing data errors, increased fees, or can be exploited to attack the application. Therefore, we need to take steps to prevent duplicate submissions.

Part 2: How to prevent duplicate submissions?

In order to prevent repeated submissions, we can take the following measures:

1. Add CSRF tokens to prevent malicious attacks.

2. Use JavaScript to verify user input on the front end to ensure that the input is legal.

3. Use JavaScript to prevent users from repeatedly submitting forms or requests.

In this article, we will focus on the third measure, which is to use JavaScript to prevent users from repeatedly submitting forms or requests.

Part 3: How to use JavaScript to check whether a request is submitted repeatedly?

In this section, we will learn how to use JavaScript to check whether a request has been submitted repeatedly.

1. In the click event of the form or link, disable the submit button or link. This prevents the user from clicking the submit button or link multiple times before the request succeeds.

2. Before submitting a form or request, use JavaScript to check whether the same request has been submitted. If so, you can prompt the user not to submit again.

The following is the code to implement the above check:

function checkIfRequestSubmitted() {
  const lastRequestTime = localStorage.getItem('lastRequestTime');
  const currentRequestTime = new Date().getTime();
  const REQUEST_TIME_DELAY = 3000; // 3 seconds

  if (lastRequestTime && currentRequestTime - lastRequestTime < REQUEST_TIME_DELAY) {
    return true;
  }

  localStorage.setItem(&#39;lastRequestTime&#39;, currentRequestTime);
  return false;
}

function submitForm() {
  const form = document.getElementById(&#39;myForm&#39;);

  if (checkIfRequestSubmitted()) {
    alert(&#39;请不要重复提交！&#39;);
    return;
  }

  form.submit();
}

The above code uses localStorage to store the time of the most recent request. If the difference between the current time and the last request time is less than 3 seconds, the request is considered to have been submitted. Otherwise, update the time of the last request and perform the commit operation.

Finally, we need to call the submitForm() function in the click event of the form or request, for example:

<button onclick="submitForm()">提交</button>

In this way, even if the user clicks the submit button or link multiple times, the JavaScript code can Check in time to prevent duplicate submissions.

Conclusion:

In this article, we discussed how to use JavaScript to check if a request is submitted twice. By disabling submit buttons or links and checking the time of the last request, we can effectively prevent repeated submissions, improve user experience and protect application security. Duplicate submission issues are common in web development, so we need to keep in mind ways to prevent duplicate submissions in order to better handle user requests.

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