Syntax Quiz - Languages JavaScript

Free practice quiz: Syntax (Languages JavaScript). 54 multiple-choice questions with answers and explanations. Play online, no sign-up needed.

This Languages JavaScript practice quiz has 54 multiple-choice questions on Syntax, and 54 of them come with an explanation. Try the 5 sample questions below (tap an option to check yourself), then play the full quiz online. No sign-up needed.

Sample questions

1. Which keyword is used to declare a variable in JavaScript that cannot be reassigned?

   1. var
   2. let
   3. const
   4. static
   Show answer

   Answer: C. const

   The `const` keyword declares a block-scoped variable whose value cannot be reassigned after its initial declaration. `var` and `let` allow reassignment.

2. Which syntax is used to access the first element of an array named `myArray` in JavaScript?

   1. myArray(0)
   2. myArray[0]
   3. myArray{0}
   4. myArray.0
   Show answer

   Answer: B. myArray[0]

   Array elements in JavaScript are accessed using zero-based indexing within square brackets `[]`.

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

   1. 6
   2. '6'
   3. NaN
   4. Error
   Show answer

   Answer: B. '6'

   JavaScript performs type coercion. When a number is added to a string, the number is converted to a string, and then string concatenation occurs.

4. How do you create a multi-line string in JavaScript without using template literals?

   1. Using backticks (` `` `)
   2. Using a backslash `\` at the end of each line
   3. Using a plus sign `+` to concatenate strings on separate lines
   4. Using single quotes `'` on each line
   Show answer

   Answer: B. Using a backslash `\` at the end of each line

   To create multi-line strings without template literals, you can use the backslash `\` at the end of a line to indicate continuation, or concatenate strings using `+` on subsequent lines.

5. What is the purpose of the `debugger` statement in JavaScript?

   1. To end program execution
   2. To create a new variable
   3. To pause JavaScript execution and trigger a debugger tool
   4. To define a function
   Show answer

   Answer: C. To pause JavaScript execution and trigger a debugger tool

   The `debugger` statement can be used to pause the execution of JavaScript code, allowing developers to inspect variables and step through the code using a debugger.

More questions in this quiz

Answers and explanations are in the full quiz.

1. What is the correct syntax for an if statement in JavaScript?
2. Which operator is used for strict equality comparison in JavaScript?
3. How do you denote a single-line comment in JavaScript?
4. What is the correct way to call a function named `myFunction` in JavaScript?
5. Which loop statement iterates over the properties of an object in JavaScript?
6. What does the `typeof` operator return for a primitive boolean value in JavaScript?
7. Which of the following is NOT a valid JavaScript data type?
8. How do you create an array with elements 1, 2, and 3 in JavaScript?
9. What is the primary purpose of the `return` statement in a JavaScript function?
10. What is the output of `console.log(typeof null)` in JavaScript?
11. Which keyword is used to define a function expression in JavaScript?
12. How do you check if a variable `x` is NOT equal to `y` using loose equality in JavaScript?
13. What does the `switch` statement in JavaScript do?
14. Which operator is used for exponentiation in JavaScript (ES6+)?
15. What is the correct syntax for a `for` loop in JavaScript?
16. Which method is used to add one or more elements to the end of an array in JavaScript?
17. What is a template literal in JavaScript (ES6+)?
18. What is the purpose of the `void` keyword in JavaScript, particularly in relation to function return values?
19. Which is the correct syntax for a `while` loop in JavaScript?
20. Which of the following is a correct way to declare a JavaScript object literal?
21. What is the purpose of the `break` statement within a loop in JavaScript?
22. Which method removes the last element from an array and returns that element in JavaScript?
23. What is the ECMAScript version that introduced arrow functions?
24. What is the correct syntax to access a property named `name` of an object `myObject` in JavaScript?
25. Which keyword is used to declare a variable in JavaScript that can be reassigned and is block-scoped?
26. What is the purpose of the `continue` statement within a loop in JavaScript?
27. What is the correct way to create a function expression in JavaScript?
28. Which of the following is NOT a valid primitive data type in JavaScript?
29. What does the `this` keyword refer to in a JavaScript method?
30. What is the correct way to declare an empty object in JavaScript?
31. What is the result of `5 == '5'` in JavaScript?
32. Which loop is guaranteed to execute its block of code at least once?
33. What is the purpose of `Object.keys()` in JavaScript?
34. Which is NOT a valid way to declare a variable in JavaScript?
35. What is the output of `console.log('JavaScript'[2])`?
36. What does the spread syntax (`...`) do when used with arrays?
37. Which of the following is a valid identifier name in JavaScript?
38. What is the result of `NaN === NaN` in JavaScript?
39. Which method is used to add one or more elements to the beginning of an array in JavaScript?
40. How do you declare a block of code that can be reused and performs a specific task in JavaScript?
41. What is the primary difference between `let` and `var` in JavaScript regarding scope?
42. Which operator is used for assignment in JavaScript?
43. What does the `&&` operator represent in JavaScript conditional statements?
44. How do you get the number of characters in a string `myString` in JavaScript?
45. Which statement is used to define a constant variable that cannot be reassigned in JavaScript?
46. What is the result of `typeof undefined` in JavaScript?
47. Which of the following is the correct syntax for a `for...of` loop in JavaScript (ES6+)?
48. What is the purpose of the `else` statement in an `if...else` structure in JavaScript?
49. How do you check if a variable `x` is strictly NOT equal to `y` in JavaScript?

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