Advanced JS

Question 1

What is Array.prototype.filter useful for?

Answer 1

Creating a new array while excluding some elements

Question 2

What is Array.prototype.map useful for?

Answer 2

Creating a new array containing the transformed elements of another

Question 3

What is Array.prototype.reduce useful for?

Answer 3

Combining the elements of an array into a single value.

Question 4

What are the three states a Promise can be in?

Answer 4

pending (initial state), fulfilled, rejected

Question 5

How do you handle the fulfillment of a Promise?

Answer 5

promise.then(),

Question 6

How do you handle the rejection of a Promise?

Answer 6

promise.catch()

Question 7

What is a promise?

Answer 7

The Promise object represents the eventual completion (or failure) of an asynchronous operation and its resulting value.

Question 8

What does fetch() return?

Answer 8

a promise containing response object

Question 9

What is the default request method used by fetch()?

Answer 9

get

Question 10

How do you specify the request method (GET, POST, etc.) when calling fetch?

Answer 10

inside the optional init object as a second argument to fetch()

Question 11

spread operator (…)

Answer 11

• used to split up array elements OR object properties
• ‘pulls out’ the elements (otherwise the entire array or object is placed)
• makes a COPY of the properties in an object, not a reference
• ex 1: (will add items in old array to new array)
  const newArr = […oldArr, 1, 2]
• ex 2: (pulls out properties and values from old object and adds to new object, BUT if they have same property, new property would override old property)
  const newObj = {…oldObj, newProp: 5}

Question 12

rest operator (…)

Answer 12

• used to merge a list of function arguments into an array
• ex: (turns args => [ ])
  function sortArgs(…args) {
  return args.sort();
  }