Moringa JavaScript Arrays

Which of the following is not false?

• JavaScript arrays are resizable and can contain a mix of different data types.

• JavaScript arrays are not associative arrays and are zero-indexed.

• Methods used to create copies i.e spread-syntax, slice(), concat(), and Array.from() methods create shallow copies of the array.

• JavaScript arrays are not objects but their own primitive types.

How do you create an array in JavaScript?

• const fruits = ['Apple', 'Banana'];

• const fruits = new Array('Apple', 'Banana');

• const fruits = 'Apple, Banana'.split(', ');

• const fruits = [];

  fruits[0]= 'Apple';

  fruits[1] = 'Banana';

The ___ Array object property gives us the count of items in an Array.

Which of the following code will return `undefined` using the following array?

const fruits = ['Apple', 'Banana'];

• fruits[-1];

• fruits[fruits.length - 1];

• fruits[1];

• fruits[0];

The ___ method is used to find the position (index) of the string "Banana" in the array;

const fruits = ['Apple', 'Banana'];

The following lines of code are used to check if an item exists. What is the result of the expression?

const fruits = ['Apple', 'Banana'];

fruits.includes('Banana') === fruits.indexOf('Banana') !== -1;

• true

• false

Which of the following correctly loops through the Array?

const fruits = ['Apple', 'Mango', 'Cherry'];

• for (const fruit in fruits) {

  console.log(fruit);

  }

• fruits.forEach(function(fruit, index, array) {

  console.log(fruit);

  });

Which of the following is false about iterating through arrays?

• The Array find() method returns the index of the 1st element that satisfies the provided testing function. If no values satisfy the testing function, -1 is returned.

• The Array filter() method creates a new array with all elements that pass the test implemented by the provided function.

• The Array reduce() method executes a callback function on each element. The final result of running the reducer across all array elements is a single value.

• The Array map() method creates a new array populated with the results of calling a provided function on every element in the calling array.

The Array.___() method determines whether the passed value is actually an array

What is the output of the following code?

const letters = ['A', 'B', 'A', 'C', 'B'];

console.log([...new Set(letters)]);

• ['A', 'B', 'C']

• [['A', 'A'], ['B', 'B'], ['C']]

• [['A', 'A'], ['B', 'B'], 'C']