JavaScript Basics Quiz (Medium)

Which declaration prevents re-assignment of the variable?

• var
• let
• const
• let const
• None of the above

Which one correctly generates a random number between 1 and 10 (inclusive)?

• Math.random(1,10)
• Math.floor(Math.random() * 10)
• Math.floor(Math.random() * 10) + 1
• Math.ceil(Math.random() * 10)
• Math.round(Math.random() * 10)

What is the output of '5' + 3?

• 8
• 53
• None of the above
• Error
• undefined

Which DOM method is used to access the element with id='score'?

• getElementsByClassName('score')
• querySelector('.score')
• getElementById('score')
• querySelector('#score')
• getElementsByName('score')

What will the following return: typeof NaN?

• number

• NaN

• undefined

• object

• null

Which of the following are falsy values in JavaScript?

• None of the above
• 0
• undefined
• None of the above
• All of the above

What is the correct way to attach a click event to a button in JS?

• button.onClick(play());
• button.addEventListener('click', play);
• addEventListener(button, 'click', play);
• onClick(button, play);
• click(button, play);

A user enters text in an input box. How can you prevent the default form submission?

• event.preventDefault()
• return false;
• throw Error()
• input.preventDefault()
• submit.prevent()

Which loop will run infinitely if the condition is always true?

• for loop with i++
• forEach loop
• while(true)
• do-while(false)
• for...of

You are building a guessing game. Which condition correctly checks if the guess is equal to the target number?

• if (guess = target)
• if (guess === target)
• if (guess ==! target)
• if (target = guess)
• if (guess != target)