Q
What does console.log() output when logging an undefined variable?

Answer & Solution

Answer: Option Option B
Solution:
When logging an undefined variable using console.log(), the output will be 'undefined'. This indicates that the variable has not been assigned a value or does not exist in the current scope. It is different from an empty string, null, or an error message, as 'undefined' is a specific value in JavaScript that represents the absence of a value for a variable. Logging undefined variables using console.log() is useful for debugging and identifying variables that need initialization or assignments in the code.
Related Questions on Average

Which method can be used to log warning messages in JavaScript?

A). console.debug()

B). console.info()

C). console.warn()

D). console.error()

How does console.log() handle logging objects with nested properties?

A). It prints only the top-level properties of the object.

B). It converts the object and all nested properties into string representations.

C). It displays an error message for objects with nested properties.

D). It ignores nested properties and logs the object structure only.

How is console.log() used to display variable values in the console?

A). By concatenating variables with strings.

B). By using special escape characters.

C). By including variables directly in the parentheses.

D). By using HTML tags.

How can you include JavaScript expressions in console.log() messages?

A). By enclosing expressions in backticks (`) within the message string.

B). By using special symbols like %s and %d.

C). By wrapping expressions in square brackets [].

D). By assigning expressions to separate log methods.

What is the recommended approach for handling console logs in production code?

A). Disable all console logs in production code.

B). Include detailed console logs for all scenarios.

C). Use conditional logging and minimize excessive logging.

D). Log all errors and exceptions using console.error().

What is the purpose of using console.log() for debugging JavaScript code?

A). To optimize code execution.

B). To log errors and exceptions.

C). To display messages to users.

D). To track variables, values, and program flow.

How can you log messages with different log levels using console.log()?

A). By using conditional statements to differentiate log levels.

B). By passing a log level as an argument to console.log().

C). By using multiple console.log() methods with different names.

D). By including log level prefixes in the message strings.

What is the behavior of console.log() when logging null or empty values?

A). It logs an empty string for null values and does not log empty values.

B). It logs 'null' or 'undefined' for null or empty values, respectively.

C). It ignores null or empty values and logs the rest of the message.

D). It displays an error message for null or empty values.

What happens if you include console.log() statements inside a loop with a large number of iterations?

A). It has no impact on script performance.

B). It significantly slows down script execution.

C). It optimizes loop execution for faster processing.

D). It automatically optimizes console logging for loops.

How can you format log messages using console.log() to include variable values or expressions?

A). By using special symbols like %s and %d in the message string.

B). By enclosing expressions in backticks (`) within the message.

C). By concatenating variables directly in the parentheses.

D). By assigning expressions to separate log methods.