JavaScript Developer Tips u0026 Tricks Quiz

Test your knowledge of essential JavaScript developer tips and tricks with this quiz designed to boost your coding efficiency and accuracy. Discover key JavaScript concepts, practical shortcuts, and best practices in a fun, easy way.

1. Choosing the Right Variable Declaration

   When declaring a variable that will never be reassigned, which JavaScript keyword should you use for better code safety?

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

   Explanation: The 'const' keyword is used for variables whose values should not be reassigned, promoting safer and clearer code. 'let' is also a modern keyword, but allows reassignment, which can lead to mistakes. 'var' is an older way that has function scope and more risks of unexpected behaviors. 'static' is not a variable declaration keyword in JavaScript.

2. Concise Array Copying

   Which modern syntax allows you to quickly make a shallow copy of an array in JavaScript?

   1. ...array
   2. array.copy()
   3. array.slice()
   4. array.push()

   Explanation: Using the spread operator '...array', placed inside new square brackets, creates a concise shallow copy of an array. 'array.slice()' also copies arrays but is longer and less modern than the spread operator. 'array.copy()' is not a built-in method. 'array.push()' adds elements to an array instead of copying it.

3. Default Function Parameters

   How can you set a default value for a parameter in a JavaScript function?

   1. function(a = 2)
   2. function(a == 2)
   3. function(a, 2)
   4. function a: 2

   Explanation: Setting a default value like 'function(a = 2)' allows the parameter 'a' to default to 2 if no argument is provided. 'function a: 2' is incorrect syntax. 'function(a, 2)' suggests two parameters, not a default value. 'function(a == 2)' wrongly uses a comparison operator instead of assignment.

4. Quick Object Property Assignment

   When creating an object with variable names matching property names, what shortcut can you use?

   1. {x = x, y = y}
   2. {x u003E y}
   3. {x: x, y: y}
   4. {x, y}

   Explanation: The shorthand '{x, y}' creates object properties with the same names as the variables x and y. '{x: x, y: y}' is correct but more verbose. '{x = x, y = y}' implies assignment, which is not valid object syntax. '{x u003E y}' performs a comparison and is not an object.

5. Template Literals Usage

   What feature allows you to include variables inside strings in JavaScript, as in 'Hello, ${name}!'?

   1. escape syntax
   2. String.concat
   3. Template literals
   4. Single quotes

   Explanation: Template literals (backticks and ${}) enable embedded variables inside strings. Single quotes do not support this feature directly. 'String.concat' combines strings but does not allow variable interpolation inside. 'escape syntax' is unrelated to including variables in strings.

6. Understanding Strict Equality

   Which operator should you use in JavaScript to check both value and type equality between two variables?

   1. ==
   2. ===
   3. =
   4. =u003E

   Explanation: The '===' operator checks for both value and type equality, making it more precise and safer than '==', which only checks value after type conversion. '=' is the assignment operator, not for comparison. '=u003E' is used for writing arrow functions, not comparisons.

7. Array Destructuring Made Easy

   Which syntax lets you assign the first two elements of an array to individual variables in one line?

   1. [a, b] = array
   2. array -u003E [a, b]
   3. array(a, b)
   4. {a, b} = array

   Explanation: The syntax '[a, b] = array' allows destructuring, assigning the first two elements to 'a' and 'b'. 'array(a, b)' is not proper destructuring and would cause an error. 'array -u003E [a, b]' is invalid in JavaScript. '{a, b} = array' is object destructuring, not array destructuring.

8. Falsy Value Check Shortcut

   If you want to execute code only if a variable 'input' is not empty, null, or undefined, which is the most concise way to check this?

   1. if(input)
   2. if(input != null)
   3. if input {}
   4. if(input === '')

   Explanation: Using 'if(input)' is concise and checks if 'input' is truthy, which excludes empty strings, null, undefined, 0, NaN, and false. 'if(input != null)' checks only for null and undefined. 'if(input === '')' targets empty strings specifically. 'if input {}' is not valid JavaScript syntax.

9. Using Short-Circuit Evaluation

   How can you provide a default value for a variable 'username' if it's undefined, in one line?

   1. username = 'Guest' u0026u0026 username
   2. username =u003E 'Guest'
   3. username u0026u0026 'Guest'
   4. username || 'Guest'

   Explanation: The expression 'username || 'Guest'' returns 'username' if it's truthy, otherwise it defaults to 'Guest'. 'username u0026u0026 'Guest'' returns 'Guest' only if 'username' is truthy, which is not suitable for defaults. 'username =u003E 'Guest'' is not correct syntax. 'username = 'Guest' u0026u0026 username' does not assign the desired value properly.

10. Quickly Removing Array Duplicates

    What is a fast way to remove duplicate values from an array called 'arr' in JavaScript?

    1. Array.from(new Set(arr))
    2. arr.unique()
    3. arr.removeDuplicates()
    4. arr.distinct()

    Explanation: 'Array.from(new Set(arr))' leverages the Set object, which stores unique values, and converts it back into an array. 'arr.unique()' and 'arr.removeDuplicates()' are not standard array methods in JavaScript. 'arr.distinct()' is not a built-in function either and would result in an error.