Homework Quiz Review & Solutions

Intermediate Functions

1. Which of the following types is mutable?

   • Answer: Array
   • Arrays are mutable. Booleans, Numbers, and Strings are immutable.

2. When is an object considered mutable?

   • Answer: If it can be changed.
   • A mutable object can be changed. An immutable object cannot be changed.

3. let arr = ["a", "b", "c", "d", "e", "f"];
   arr.splice(2, 3);
   console.log(arr);

   What will the code snippet above print out?
   • Answer: [‘a’,‘b’,’f]
   • Array#splice mutates the input array, removing 3 elements starting at index 2.

4. Which of the following best describes the ordered arguments that Array#splice accepts?

   • Answer: targetIndex, removeAmount, insertionItem1, insertionItem2, …
   • Array#splice accepts a target index, the number of elements to remove starting at that index, and any number of additional arguments to be inserted at that index

5. Which of the following best describes why objects are considered “first-class” in JavaScript?

   • Answer: can be stored in variables
   • A first-class object is something that can be stored in a variable.

6. let sayHello = function () {
     console.log("hello");
   };

   Which of the following best describes the code above?

   • Answer: Function Expression Syntax
   • Assigning a variable to a function is “function expression” syntax.

7. Which of the following methods does not mutate their input?

   • Answer: Array.splice
   • The slice method does not mutate, instead it returns a copy. The remaining methods all mutate their input

8. let arr = ["a", "b", "c", "d", "e"];
   arr.slice(1, 3);
   console.log(arr);

   ** What will the code snippet above print out?**
   • Answer: [‘a’, ‘b’, ‘c’, ‘d’, ‘e’]
   • Array#slice does not mutate the input array, so arr is unchaged.