HTML `datalist` with ghost effect on Chrome for Android

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Summary

The issue at hand is related to the HTML datalist element and its behavior on Chrome for Android. When using a dynamic datalist to simulate a search function with AJAX, the list of suggestions sometimes gets stuck or frozen with old results, and in some cases, exhibits a ghost effect where the old results appear half-transparent. This problem is specific to Chrome on Android devices and does not occur on PC.

Root Cause

The root cause of this issue can be attributed to several factors, including:

  • Chrome for Android’s rendering engine: The way Chrome for Android handles the rendering of dynamic datalist elements might be flawed, leading to the stuck or frozen suggestions.
  • Event handling and timing: The use of setTimeout and the keyup event listener might be causing timing issues that contribute to the problem.
  • DOM manipulation: The continuous removal and addition of option elements to the datalist might be causing the browser to struggle with updating the UI correctly.

Why This Happens in Real Systems

This issue occurs in real systems due to the combination of the following factors:

  • Mobile browser limitations: Mobile browsers like Chrome for Android have limited resources and might not handle complex DOM manipulations as smoothly as their desktop counterparts.
  • Dynamic content: The use of dynamic content, such as the datalist element, can be challenging for browsers to render correctly, especially when combined with event listeners and timeouts.
  • User interaction: The specific sequence of user interactions, such as typing, pressing backspace, and waiting for a few seconds, can trigger the issue.

Real-World Impact

The impact of this issue is primarily user experience-related, as it can cause frustration and confusion for users who expect the search suggestions to update correctly. The ghost effect can also make the UI appear broken or glitchy, which can negatively affect the overall perception of the application or website.

Example or Code

function clearDatalist(datalistHTML) {
  if (typeof(datalistHTML) !== 'object') {
    return;
  }
  while (datalistHTML.firstChild) {
    datalistHTML.removeChild(datalistHTML.lastChild);
  }
}

async function doKWSuggestion(event) {
  const inputValue = event.target?.value;
  const dataList = document.getElementById('keywords');
  const optionsArray = ['apple', 'appear', 'google', 'youtube', 'amazon', 'amazing'];
  clearDatalist(dataList);
  await delay(1000);
  optionsArray.forEach((item) => {
    if (item.toLowerCase().includes(inputValue.toLowerCase())) {
      const option = document.createElement('option');
      option.value = item;
      dataList.appendChild(option);
    }
  });
}

How Senior Engineers Fix It

To fix this issue, senior engineers might employ the following strategies:

  • Use a different approach for rendering suggestions: Instead of using a datalist element, consider using a div or ul element to render the suggestions, and update the content using JavaScript.
  • Optimize event handling and timing: Review the event listeners and timeouts used in the code and optimize them to reduce the likelihood of timing issues.
  • Minimize DOM manipulation: Reduce the number of times the DOM is manipulated by batching updates or using more efficient methods for updating the suggestions.

Why Juniors Miss It

Junior engineers might miss this issue due to:

  • Lack of experience with mobile browsers: Junior engineers might not be familiar with the quirks and limitations of mobile browsers, which can lead to overlooking potential issues.
  • Insufficient testing: Junior engineers might not thoroughly test their code on different devices and browsers, which can cause them to miss issues like this one.
  • Overreliance on desktop debugging: Junior engineers might focus too much on debugging their code on desktop browsers and neglect to test it on mobile devices, where the issue is more likely to occur.