MTEC1003 - Prep, Review

Git - Setting up Repositories

What command would you use to clone a remote repository? →

# clone a remote repo

git clone https://your_username/your-repository-name.git

What is the command to show a remote repo? →

# show remote repositories
git remote -v

# The output should look something like...
# origin  https://bzuckerman@github.com/bzuckerman/lab-08-prep.git (fetch)
# origin  https://bzuckerman@github.com/bzuckerman/lab-08-prep.git (push)

...continued...

Git - Setting up Repositories Continued

What command would you use to configure your cloned repository with your name and email? →


# configure it with your name and email
git config user.name  "your name"
git config user.email "your@email.address"

What’s are the commands that you would use for making, saving and sharing changes? Let’s start with just making the change and prepping it to be saved. →

# (make changes)

# show the exact, line-by-line changes that you've made
git diff --color

# check on the status of your changes
git status

# stage your changes / prep them to be saved
git add --all 

# check your staged changes using git status again
git status

# (continued...)

Saving and sending to the remote repository →

# save them, make sure you remember your comment by using -m!
git commit -m 'my message'

# show a history of your changes
git log --color (show your changes so far)

# send to your remote repository
git push origin master

A Template

What kind of file and what set up do we have write in order to start a new JavaScript program? →

We have to create a bare bones web page, an .html file:

<!DOCTYPE html>
<html>
<body>
<script>
// your JavaScript goes here!
</script>
</body>
</html>

Your code goes within the script tags!

Data Types and Values

What’s a value and what’s a data type? →

values are just data - for example: 3.14, “hello”
a type is just a kind or category of value.

Data Types

What are some data types that we know? →

number - numeric data (clearly!)
string - an ordered sequence of characters (alphanumeric, punctuation, spaces, etc.)
boolean values - true / false
there’s also undefined… when we try to use a variable that hasn’t been created yet

Numbers

Numbers can be positive or negative rational numbers, like 23, -42 and 3.14. However, there are also some special values that are numbers. →

Infinity, -Infintity - positive and negative infinities (don’t use these, they’re not that useful, and not mathematically solid!)
NaN (not-a-number) - this results from any numeric operation that doesn’t give back a meaniigful result… such as 0/0

Strings

What’s a string, and give an example of a string literal →

A string is an ordered sequence of characters. You can tell that a value is a string if it is surrounded by single or double quotes:

"Surrounded by quotes!"

What kind of data type is this? → "5"

It's a string!

"When numbers are surrounded by quotes they are strings!"

Escape Characters

How do we write a backslash, quote, tab or a new line in a string? →

use the escape character, backslash (\)
if there is a backslash in a string (\), it means:
- the next character has a special meaning
- the initial backslash will not be printed out
for example, backslash, quote, tab and newline:

"\\"
"\""
"\t" 
"\n"

Booleans

What’s a boolean value? →

A boolean value is a data type with only two possible values:

true
false

Operators

What’s an operator and what are some examples of operators? →

operators allow us to combine and transform values
operators have operands,
- operands are the values that supplied to operators
- binary operators have two operands
- unary operators have one operand
operators give back values
- using operators with values yields other values!
examples: + - * / % (these are numeric operators)

String Operators

We learned one operator that works on strings. What was it? →

string concatenation, or +, is an operator that takes two strings and joins them:

"hello " + "there"

What is the result of this expression? →

"1" + "1"

Comparison Operators

Name some comparison operators that return boolean values… →

=== - equals - checks if both operands are the same value and type
- gives back true if both are the same value and type
- gives back false otherwise
!== - not equals - checks if the operands are not the same value or type
- gives back true if both operands are not the same value or type
- gives back false otherwise

Logical Operators

Name some logical operators that allow you to combine boolean values. →

and (represented as &&) - takes two operands.
- only gives back true when both operands are true.
- gives back false otherwise
or (represented as ||) - takes two operands.
- returns true if either operand is true
- it only gives back false when both operands are false.
they are evaluated left to right (precedence is determined left to right)

Boolean Expressions

You can create boolean expressions with comparison and logical operators. What is the value that results from the following expressions? →

24 !== "hello"
5 === "5"
true && false
false || true

true
false
false
true

More Boolean Expressions

false && true || true
false && (true || true)
5 < 2 || 8 > 20

var login = "albert";
var password = "secret";
login === "albert" && password === "secret"

true
false
false
true

Not

There’s one more logical operator, not.

only takes one operand, a boolean
gives back the opposite boolean value
not is represented by an exclamation point - !

! true
! (5 > 10)
! (true && true)

false
true
false

Unary Operators

Unary Operators only have a single operand to the right:

+ - convert to positive number
- - convert to negative number

What’s the operator that gives back the type of a value? →

typeof - gives the type of a value (Number, String, etc.)

typeof

Again, typeof is:

an operator that takes one operand
gives back the type of value the operand

What would we get with this code: →

typeof -12
typeof "98.6"
typeof (20 === 20)
typeof NaN

number, string, boolean, number

Functions

What’s a function? What’s a function call? What are arguments? →

a function is a named sequence of statements that perform some useful action
it can optionally take inputs and return values
to call a function is just to run or execute it
the values passed to a function are called arguments

Calling Functions

How do you call or execute a function? →

to call a function, use its name followed by parentheses… with an optional list of comma separated arguments between the parentheses
an example of a function call is:

prompt("What is your name?")

Built-in Functions

JavaScript comes with many built-in functions. We know three; what are they and what do they do? →

prompt(“some message”) - asks the user for input and returns that value to your program! … takes an argument, the message to display to a user (this usually requires the use of variables)
console.log(“some message”) - prints the argument that you pass to it… out to Chrome’s JavaScript console
parseInt(“5”) - converts a string to a number

Some Functions Return Values

What type of value does prompt always return? What type of value does parseInt always return? →

prompt always gives back a string
parseInt always gives back a number

Using Prompt With Variables

Remember that the function prompt gives back a value. To retain that value, you have to hold it in a variable:

var answer = prompt("Yes or no!?");

Blocks of Code

Curly braces denote statements of code that are grouped together. Everything within the curly braces below is considered part of the if statement. Blocks of code must start and end with curly braces…

... {
	// code wrapped by curly braces
}

Conditionals…

What kind of statement would we use to execute code if a condition is true? →

An if statement…

if (some_boolean_expression) {
	// do stuff here if expression is true
}

Conditionals Continued

What kind of statement would we use to execute code one branch of code if a condition is true and another branch of code otherwise? →

an if / else statement
an else must always have a preceding if!

if (some_boolean_expression) {
	// do stuff here if expression is true
} else {
	// do stuff here if expression is false
}

If / Else If

What kind of statement would we use to execute multiple branches of code based on multiple chained conditions? →

Use if / else if statements

if (boolean_expression_1) {
	// do stuff here if expression 1 is true
} else if (boolean_expression_2) {
	// do stuff here if expression 2 is true
} else if (boolean_expression_3) {
	// do stuff here if expression 3 is true
}

If / Else If

once a condition is true, the if / else if executes the code in that block and the if / else if ends immediately (even if other later conditions are true)
can end with else to handle all other conditions

Usage

use if statements if there’s a single alternative path of execution
use if/else statements if there’s a two possible alternative paths of execution
use if/else if statements if there’s more than two possible alternative paths of execution

Repeat That Again?

What construct do we use if we want to execute a block of code multiple times without writing it multiple times? →

we use a for loop!
what does a for loop look like… what are its parts? →

For Loop Dissected

A for loop consists of the keyword, for, and three parts, separated by a semicolon, contained within parentheses:

initialization - declares a variable and value to start with
condition - a condition for the loop to stop
afterthought - a way to increment/decrement or change the variable on each iteration so that the condition is eventually met

You can use the variable that you declare in the initialization within your for loop!

For Loop Parts

//    initialization
//    |        condition
//    |        |       afterthought/increment
//    |        |       |
for(var i = 0; i <= 5; i = i + 1) {
	console.log(i);
}

Counting By 3’s

Create a for loop that counts from 0 up to and including 9 by 3’s? →

for(var i = 0; i <= 9; i = i + 3) {
	console.log(i);
}

Prep, Review

Quick Rundown of Git Commands

Git - Setting up Repositories

Git - Setting up Repositories Continued

Git - Saving and Sharing Changes

Git - Saving and Sharing Continued…

JavaScript

A Template

Data Types and Values

Data Types

Data Types

Numbers

Strings

Escape Characters

Booleans

Operators

String Operators

Comparison Operators

Even More Comparison Operators

Logical Operators

Boolean Expressions

More Boolean Expressions

Not

Boolean Expressions Give Back Boolean Values!

Unary Operators

typeof

Functions

Calling Functions

When you see parentheses - ( )’s - after a function name, that function is being called or executed

Built-in Functions

Some Functions Return Values

Using Prompt With Variables

Conditionals

Blocks of Code

Conditionals…

Conditionals Continued

If / Else If

If / Else If

Usage

Repeat That Again?

For Loop Dissected

For Loop Parts

Counting By 3’s