JavaScript Fundamentals Part 2

Last year, I continued studying on Fundamentals of Javascript in the Odin Project Web Development 101. I decided to start off the New Year by doing a review of what I had studied a month ago.

I did the first JavaScript “Test Yourself” questions in this blog post.

These are the second JavaScript “test yourself” questions here and my answers below.

  • What are the seven data types of javascript?
  1. Number
  2. String
  3. Boolean
  4. Null
  5. Undefined
  6. Object
  7. Symbol
  • Which data type is NOT primitive?

Object.
This is because objects store collections of data and more complex entities.
Whereas, numbers, strings, booleans, null, undefined, and symbol are represented directly. Also, those data types cannot be changed (although, the variables they may be stored in can change).

  • What is the difference between single, double, and backtick quotes for strings?

Single and double quotes are the same. But they need to be used consistently, not mixed – ‘Hi’ or “Hi”
not “Hi’

Backtick quotes are extended functionality quotes. They allow us to embed variables and expressions into a string using  backticks:
stringtext ${variable} stringtext `

  • Which type of quote lets you embed variables/expressions into a string?

Backticks.

  • How do you embed variables/expressions into a string?

Using the dollar sign and { } brackets together.
The variable or expression would be written within the curly brackets.

  • How do you escape characters in a string?

​​​​​You can escape characters, like a  single, double, or backtick quote with a backslash before them \’ \” \`

  • What is the difference between slice/substring/substr?

These are three ways to extract part of a string.
The parameters are different in each:

  1. slice(start, end)
  2. substring(start, end)
  3. substr(start, length)

Slice extracts part of a string and returns the extracted part in a new sting.
Substring is similar to slice. Substr is different because you choose the length of the string you want to get, rather than the end point of the original string.

  • What are methods?

A method is a bit of functionality that is built into the language. They are properties which contain a function. So, slice(), substring(), and substr() are methods.
Also, indexOf() and search() are methods.

  • What are the three logical operators and what do they stand for?

&& AND

|| OR

! NOT

  • What are the comparison operators?

> greater than
< less than
>= greater than or equals
<= less than or equals
== equality check
!= not equals

  • What is nesting?

When we put something inside something else.
In JavaScript, we can nest if statements within each other. For example,
if (condition) {
xyz } else if (condition) {
zyx } else {
abc }

  • What are truthy and falsy values?

A value that evaluates as true in a Boolean context is truthy.
A value that evaluates as false in a Boolean context is falsy.

  • What are the falsy values in Javascript?
  1. false
  2. undefined
  3. null
  4. 0
  5. NaN
  • What is the syntax for an if/else if/else conditional?

if (condition) {
xyz } else if (condition) {
zyx } else {
abc }

  • What is the syntax for a switch statement?

switch (expression) {
case choice 1:
run this code
break;
case choice 2:
run this code
break;
default:
actually, just run this code
}

  • What is the syntax for a ternary operator?

(condition) ? run this code : run this code instead;

  • What is the relationship between null and undefined?

Null is a value. It means “nothing, empty, no value”.
Whereas, Undefined means there is a variable but “value has not been assigned”.

If you test equality:
null == undefined would be true
null === undefined would be false

This is because with strict equality they need to be the same type to return true. Null is an object, but undefined is a type of value itself.

  • What are conditionals?

Conditionals are statements which execute a block of code is certain conditions are true.
Conditional statements include:

  1. if
  2. else
  3. else if
  4. switch

 

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