Is `console.log()` Asynchronous or Synchronous: Fact or Fiction?

The Mysterious Case of console.log(): Async or Sync?

Trevor Burnham's Async Javascript book claims that console.log() is an asynchronous function in Safari and Chrome. However, a simple code test reveals that it appears to behave synchronously. Does this mean the book's information is outdated, or is there more to the story?

What the Book Says

Burnham's book asserts that console.log() is placed in the event queue after the code execution and executed once the queue is empty. This would mean that any changes made to the logged variable after console.log() has been called should be reflected in the output.

Testing the Hypothesis

The example code provided in the question demonstrates that console.log() is not exhibiting asynchronous behavior. When an object is logged before adding a property to it, the output shows the original empty object, not the updated object with the added property.

Unveiling the Truth

console.log() is not standardized, allowing browsers to define its behavior independently. This means the information provided in the book may not be accurate for current browser versions.

Implications for Developers

Regardless of whether console.log() is asynchronous or not, it does not offer any callback mechanism or alter the evaluation of passed values. Therefore, it makes no practical difference to code behavior.

Console Behavior

However, the console itself may implement optimizations to enhance its functionality. It may clone or store references to logged objects, enabling interactive inspections of mutable objects. This can lead to the apparent asynchronous behavior observed when expanding logged objects.

Workarounds and Best Practices

To ensure consistent behavior, consider serializing logged objects using JSON.stringify() or utilizing breakpoints for debugging, which provide a more reliable way of examining current object values.

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