Getting Started with Programming

Computers only speak certain languages, like the one you've been using today: JavaScript!

Editor and comments

The// sign is for comments. A comment is a line of text that JavaScript won't try to run as code. It's just for humans to read.

Comments make your program easier to understand. When you look back at your code or others want to collaborate with you, they can read your comments and easily figure out what your code does.

What am I learning?

This is JavaScript (JS), a programming language. There are many languages, but JS has many uses and is easy to learn.

What can we use JavaScript for?

• make websites respond to user interaction

• build apps and games (_e.g._blackjack)

• access information on the Internet (e.g. find out the top trending words on Twitter by topic)

• organize and present data (_e.g._automate spreadsheet work; data visualization)

confirm('This is an example of using JS to create some interaction on a website. Click OK to continue!');

Interactive JavaScript

confirm("I feel awesome!");

confirm("I am ready to go.");

These boxes can be used on websites to confirm things with users. You've probably seen them pop up when you try to delete important things or leave a website with unsaved changes.

See the Example

What is programming?

Programming is like writing a list of instructions to the computer so it can do cool stuff with your information.

To do any of actions, the program needs an input. You can ask for input with a prompt.

Examples:

prompt("What is your name?");

prompt("What is Ubuntu?")

Data Types I & II: Numbers & Strings

Data comes in various types. You have used two already!

a. numbers are quantities, just like you're used to. You can do math with them.

b. strings are sequences of characters, like the letters a-z, spaces, and even numbers. These are all strings: "Ryan", "4" and "What is your name?" Strings are extremely useful as labels, names, and content for your programs.

To make a number in your code, just write a number as numerals without quotes: 42, 190.12334.

To write a string, surround words with quotes: "What is your name?"

Data Type III: Booleans

booleans. A boolean is either true or false.

For example, comparing two numbers returns a true or false result:

• 23 > 10 is true

• 5 < 4 is false

Using console.log

console.log()will take whatever is inside the parentheses and log it to the console below your code—that's why it's called console.log()!

Comparisons

List of comparison operators:

• > Greater than

• < Less than

• <= Less than or equal to

• >= Greater than or equal to

• === Equal to

• !== Not equal to

Here is an example of using the greater than (>) operator:

See the Example

Decisions, decisions

An if statement is made up of the ifkeyword, a condition like we've seen before, and a pair of curly braces { }. If the answer to the condition is yes, the code inside the curly braces will run.

if( "myName".length >= 7 ) {

    console.log("You have a long name!");

}

We used an if statement to do something if the answer to the condition was yes, or true as we say in JavaScript.

In addition to doing something when the condition is true, we can do something else if the condition isfalse.

if( "myName".length >= 7 ) {

    console.log("You have a long name!");

}

else {

    console.log("You have a short name!");  

}

Math and the modulo

When % is placed between two numbers, the computer will divide the first number by the second, and then return the remainder of that division.

Modulo and if \/ else

if( 15%3 == 0 ) {

    console.log("The first number is even");

} else {

    console.log("The first number is odd");

}

Substrings

Sometimes you don't want to display the entire string, just a part of it.

Code:

"some word".substring(x, y) where x is where you start chopping and y is where you finish chopping the original string.

"hello". substring(0, 2);

Variables

To do more complex coding, we need a way to 'save' the values from our coding. We do this by defining a variable with a specific, case-sensitive name.

Once you create (or declare) a variable as having a particular name, you can then call up that value by typing the variable name.

var varName = data;

See the Example

A variable's value is easily changed. Just pretend you are creating a new variable while using the same name of the existing variable

 var myAge ="23";

        console.log(myAge);

        myAge="24";

        console.log(myAge);