Javascript array stores values twice when menu editor runs for first time

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Summary

The issue described involves a Javascript array storing values twice when a menu editor runs for the first time. Despite the function call being executed only once, the array ends up containing two values instead of the expected empty or single value state.

Root Cause

The root cause of this issue is not explicitly stated in the provided information, but it can be inferred that it might relate to how the initialization of the menuJsonState array is handled within the initMenuCanvas function, particularly when the cmcInitialized flag is set and when jsonCanvas is pushed into menuJsonState. The problem could also stem from how events are handled and when the initMenuCanvas function is called in relation to the rendering and initialization of the page components.

Why This Happens in Real Systems

In real systems, this can happen due to a variety of reasons including but not limited to:

  • Asynchronous initialization and event handling which can lead to unexpected behavior if not properly synchronized.
  • Global state variables (menuJsonState, cmcInitialized) being modified at different points in the application lifecycle, potentially by different functions or event handlers.
  • The dynamic nature of web pages, where content is loaded, and scripts are executed in a certain order that might not always be as expected.

Real-World Impact

The real-world impact of this issue could range from minor inconsistencies in the application’s behavior to more significant problems such as data corruption or security vulnerabilities, depending on how critical the menuJsonState array is to the application’s functionality and the nature of the duplication (whether it’s a simple value or a complex object with potential side effects).

Example or Code

// Example of how the issue might be mitigated by ensuring initMenuCanvas is only called once
// and that menuJsonState is properly initialized before use.
let menuJsonState = [];
let cmcInitialized = false;

function initMenuCanvas() {
  if (cmcInitialized) return;
  cmcInitialized = true;
  const jsonCanvas = getJsonContentType("div");
  jsonCanvas.lgstyle = "background-color:#ffffff;width:100%;min-height:70px;";
  // Check if menuJsonState is already initialized with the expected data
  if (menuJsonState.length === 0) {
    menuJsonState.push(jsonCanvas);
  }
}

How Senior Engineers Fix It

Senior engineers would likely approach this issue by:

  1. Reviewing the codebase to identify where and when menuJsonState is being modified and ensuring that initialization and modification logic is sound and properly synchronized.
  2. Implementing logging or debugging statements to track when and how initMenuCanvas is called and how menuJsonState is modified.
  3. Ensuring proper use of asynchronous programming techniques if the issue is related to timing of events and initialization.
  4. Considering a redesign of the global state management to avoid such issues in the future, potentially leveraging more modern state management techniques or libraries.

Why Juniors Miss It

Juniors might miss this issue due to:

  1. Lack of experience with asynchronous programming and the nuances of event handling in web applications.
  2. Insufficient understanding of how global state variables can be accessed and modified across different parts of an application.
  3. Inadequate testing and debugging practices that might not uncover such subtle issues.
  4. Overlooking the importance of properly initializing and synchronizing access to shared resources like arrays in a dynamically loaded environment.