Why Does `console.log` Show Different Child Element Counts for the Same Element in JavaScript?

console.log Conundrum: Disparate Element Length Reports

In a JavaScript environment, a perplexing situation arises when accessing element children through console.log. Consider the following scenario:

Element 1:

console.log(element1.children); // Expected behaviour
/*
 Output: [<li>...</li>, <li>...</li>]
 Length: 2
*/

Element 2:

console.log(element2.children);
/*
 Output: []
 Length: 0
*/

However, upon expanding element2 in the console, it unexpectedly reveals three child elements:

/*
 Output: [<li>...</li>, <li>...</li>, <li>...</li>]
 Length: 3
*/

The Cause: Live Object References

The key to understanding this discrepancy lies in the nature of console.log. When logging objects, the console establishes a live reference, not a snapshot. Therefore, when the object is expanded, the console displays its current state, rather than the state at the time of logging.

In this case, element2's collection is likely empty initially and then populated later.

Resolving the Issue

To resolve this issue, it is necessary to ensure that the collection is populated before logging or using it in code. This can be achieved by:

• Delaying the execution of the code until the collection is filled (e.g., by placing the script at the end of the document)
• Using a debugger to halt script execution and examine the state of the collection at a known point in time

Caveats

It is crucial to note the subtle blue (i) icon next to logged objects in the console, which displays a tooltip indicating if the displayed value is a snapshot or a recent evaluation. This can help prevent confusion.

Additionally, using a debugger provides a more comprehensive view of the script's execution and allows for greater control over the timing of events.

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