You Don't Know Js Yet (Chapter 2)

Front 1

Polymorphism

Back 1

Also known as class inheritance.

Hint 1

Related to classes

Front 2

What are some incorrect returns for strict equality ('===')?

Back 2

NaN === NaN; // false
0 === -0; // true

Hint 2

Related to numbers.

Front 3

In what case is `x === y` true?

Back 3

Both reference the same object, such as an array.

Front 4

How do you measure structural equality? For example, how can you check x and y so that they are true, where x = [1,2,3]; y = [1,2,3]?

Back 4

In Javascript, you can't. You will need to programmatically check it yourself.

Hint 4

Kind of a trick question.

Front 5

What variable does `catch` declare and what is its scope?

Back 5

`catch` declares a variable, `err`, which is a block-scoped variable that exists only inside `catch`, as if it is a `let`.

Hint 5

Think of the `let` variable's scope.

Front 6

How can you distinguish value types?

Back 6

Use the `typeof` operator.

Hint 6

Use a certain operator.

Front 7

True or false?
3 === 3.0;

Back 7

true

They share the same type and value.

Hint 7

Think about the type is each value.

Front 8

True or false?

42 === "42";

Back 8

false

One is an integer while the other is a string.

Hint 8

Keep in mind that strict equality checks both value and type.

Front 9

True or false?
42 == "42";

Back 9

true

For loose equality, the type does not need to be the same.

Hint 9

`==` is loose equality

Front 10

True or false?
1 == true;

Back 10

true

Hint 10

`==` is loose equality

Front 11

How do you import the following from `example.js` file:

export function create(title,author,pubDate) {
....
}

Back 11

import { create as semanticName } from "example.js";

or alternatively:

import create from "example.js";

Hint 11

Remember that including a semantic name is only optional.

Front 12

Why does it matter that each file is a program?

Back 12

Since JS treats files as programs, one file may fail and that does not prevent the next file from being processed.

Hint 12

What might happen if Javascript fails?

Front 13

What are the two types of values?

Back 13

primitive and object

Hint 13

We commonly speak about cave-people having a ______ society.

Front 14

Name all six primitive types

Back 14

- Boolean
- Null
- Undefined
- Number
- String
- Symbol

Hint 14

It's not exactly listed in YDKJS, so don't worry if you don't get it the first time.

Front 15

Definition of an object type?

Back 15

An unordered, keyed collection of ANY various values.

Hint 15

It's a collection of...

Front 16

Don't use `3.141592` for Pi. Instead use...

Back 16

`Math.PI`

Hint 16

It's a predefined value.