Front End Developer Mock Interview
Practice 30 Front End Developer interview questions covering HTML, CSS, JavaScript, frameworks, and performance optimization.
Question 7 of 30
Please discuss the difference between null, undefined or undeclared variables.
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William Swansen has worked in the employment assistance realm since 2007. He is an author, job search strategist, and career advisor who helps individuals worldwide and in various professions to find their ideal careers.
Another technical question asking you to discuss the differences between several terms or concepts used in this profession. To prepare for an interview, you should research the company, the products it produces, and the type of programming you're likely to encounter. You can find information about this on the company's website and in the job description. Once you understand this, you should be prepared to answer questions related to the work they do. Any answer you provide to a question should be within the context of this.
William Swansen has worked in the employment assistance realm since 2007. He is an author, job search strategist, and career advisor who helps individuals worldwide and in various professions to find their ideal careers.
"Null, undefined, and undeclared are different types and states of variables used within the JavaScript programming language. Null is a value of a variable, which is a type of object. A variable is considered undefined when declared, but no value has been assigned to it. An undeclared variable occurs when the code tries to access the variable, and it has not been initialized or declared earlier using a var or const keyword."
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Null is an actual value that's an object that you can assign to a variable.
Undefined means no value has been assigned to a variable but it has been declared.
Undeclared means the name of the variable hasn't even been defined yet using let, var, or const.
The first two will result in a false check-in of statements and the last will give a runtime error.
Amanda's Feedback
Well done! You've clearly explained each and what the results of each would be.
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