Knowledge Check · 5 minutes

JavaScript Quiz

10 questions on variables, data types, arrays, and functions. Answer them all and instantly get a result with a recommendation for what to learn next.

Question 1 of 10

What's the difference between const and let?

Nothing, they're the same✓✗ A const variable's value can't be reassigned after declaration✓✗ let only works inside functions✓✗ const is only used for numbers✓✗

Question 2 of 10

What does typeof "42" return?

"string"✓✗ "number"✓✗ "undefined"✓✗ "boolean"✓✗

Question 3 of 10

How does === differ from ==?

No difference, they work the same✓✗ === compares both value and type, with no type coercion✓✗ == is only used for strings✓✗ === only works with numbers✓✗

Question 4 of 10

How do you get a page element by a CSS selector?

document.getStyle()✓✗ document.findElement()✓✗ document.querySelector()✓✗ document.getTag()✓✗

Question 5 of 10

Which array method adds an element to the end?

array.add()✓✗ array.push()✓✗ array.append()✓✗ array.insert()✓✗

Question 6 of 10

What does array.map() do?

Removes elements from an array✓✗ Sorts the array alphabetically✓✗ Creates a new array by applying a function to every element✓✗ Checks whether an element exists in the array✓✗

Question 7 of 10

How do you declare a function that takes two arguments and returns their sum?

function sum(a, b) { return a + b; }✓✗ function sum(a, b) { print a + b; }✓✗ sum(a, b) => return a + b✓✗ function sum { a + b }✓✗

Question 8 of 10

What does console.log(2 + "2") output?

4✓✗ "22"✓✗ NaN✓✗ An error✓✗

Question 9 of 10

Which keyword is used to test a condition and run code if it's true?

loop✓✗ if✓✗ function✓✗ const✓✗

Question 10 of 10

How many times does the body of for (let i = 0; i < 5; i++) run?

4 times✓✗ 5 times✓✗ 6 times✓✗ Infinitely✓✗

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