JavaScript Basics Test

Test your understanding of JavaScript values, variables, arrays, comparisons and JSON.

6 questions. Choose the best answer for each question, then review every explanation.

Question 1 of 6

1 of 6

Question 1Which comparison checks both value and type?

=!======

Question 2Where is a variable declared with let available?

if (true) {
    let message = 'Hello';
}

Only inside the enclosing blockEverywhere in the scriptOnly inside functionsOn the window object

Question 3What does Array.prototype.map() return?

One accumulated valueOnly matching valuesA new array of transformed valuesThe original array after mutation

Question 4What is the result of typeof null?

typeof null

"object""null""undefined""boolean"

Question 5What does const prevent?

Using the value in an arrayReassigning the variable bindingChanging every property of an objectReading the variable outside a function

Question 6Which method converts a JSON string into a JavaScript value?

JSON.stringify()JSON.value()JSON.decodeText()JSON.parse()