JavaScript Fundamentals

Test your grasp of variables,data types,and basic syntax in JavaScript.

1. Which keyword is block-scoped and cannot be reassigned?

var let const

2. What is the result of 3 + '3' in JavaScript?

6 "33" 33 NaN

3. Which is NOT a primitive data type in JavaScript?

String Object Boolean Number

4. What does typeof null return?

"null" "object" "undefined" "symbol"

5. Which array method removes the last element?

push() pop() shift() unshift()

6. Select all falsy values in JavaScript:

0 "" null true "false"

7. Which are valid loop structures in JavaScript?

for while do-while foreach repeat

8. Which are valid ways to declare a function?

function greet() {} const greet = function() {} const greet = () => {} greet: function() {}

9. Which operators check for equality?

=== == = !== !=

10. Which are primitive data types?

String Number Boolean Array Symbol

11. Variables declared with 'var' are function-scoped.

True False

12. In browsers, 'this' in a global function refers to the window object.

True False

13. JavaScript is a statically typed language.

True False

14. The '===' operator compares both value and type.

True False

15. Array.prototype.map() modifies the original array.

True False

16. What is the standard file extension for JavaScript files?

17. What method converts a JavaScript object to a JSON string?

18. What keyword declares a variable that can be reassigned but not redeclared?

19. What is the output of 'typeof 42'?

20. What abbreviation refers to the global object in Node.js?

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