In certain scenarios, like when conducting tests, why is it necessary to establish the definition of "var console = window.console;"?

After running the test with PhantomJS, it is possible for the test to fail due to certain console.log issues. To address this, I have found that adding the following line at the top inside the Immediately Invoked Function Expression (IFFE) helps resolve the problem:

var console = window.console;

Initially, this seems peculiar. Isn't PhatomJS based on Webkit, where both console and console.log are already defined?

Furthermore, if window.console is already defined and we assign it using var console = window.console;, wouldn't the browser automatically use window.console when encountering console in the global environment?

I believe that if the console.log(...) statements were replaced by window.console.log(...), there would be no need for var console = window.console;.

So why is var console = window.console; necessary, and what issue does it help resolve?

javascriptphantomjs

Answer №1

If the existence of window.console is confirmed, this line will not have any impact.

In a scenario where window.console is not present, this code snippet declares the identifier console as valid within the function's scope. Without this line, using console would result in a ReferenceError, but with window.console, it simply returns undefined.

Essentially, this line establishes console only if it doesn't already exist as an identifier, or alternatively, resorts to the global console value if it does.

Based on your test environment, it appears that window.console is not defined.

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