JavaScript(1)---Introduction

INTRODUCTION TO JAVASCRIPT

(In order to get the un-ordered list go to code and put in <ul> </ul> at the front and the end of the part where you want it!)

Console

In JavaScript, the console keyword refers to an object, a collection of data and actions, that we can use in our code.  We can write comments in our code that the computer will ignore as our program runs. These comments exist just for human readers.
EX: print 'Woohoo! I love to code! #codecademy' to the console.
console.log('Woohoo! I love to code! #codecademy');
print log the number 2011 to the console.
console.log(2011);

two types of code comments

"//" single line comment
"/*  */" multi=line comment

Note: Can also use this syntax to comment something out in the middle of a line of code:

console.log(/*IGNORED!*/ 5); // Still just prints 5

• seven fundamental data types:

Number: Any number including decimals
String: Any grouping of characters on your keyboard, surrounded by single quotes: ' ... ' or double quotes " ... "
Boolean: This data type only has two possible values— either trueor falseIt’s helpful to think of booleans as on and off switches or as the answers to a “yes” or “no” question.
Null: This data type represents the intentional absence of a value, and is represented by the keyword null (without quotes).
Undefined:This data type is denoted by the keyword undefined(without quotes). It also represents the absence of a value though it has a different use than null.
Symbol:A newer feature to the language, symbols are unique identifiers, useful in more complex coding.
Object: Collections of related data.

Arithmetic Operators

An operator is a character that performs a task in our code. JavaScript has several built-in in arithmetic operators, that allow us to perform mathematical calculations on numbers. These include the following operators and their corresponding symbols:

1. Add: +
2. Subtract: -
3. Multiply: *
4. Divide: /
5. Remainder: %

EX: console.log(0.2708 * 100);

String Concatenation

This process of appending one string to another is called concatenation. Just like with regular math, we can combine, or chain, our operations to get a final result. 

EX: console.log('One' + ', ' + 'two' + ', ' + 'three!');

Properties

Every string instance has a property called length that stores the number of characters in that string. You can retrieve property information by appending the string with a period and the property name. 

EX: console.log('Hello'.length);

In the example above, the value saved to the length property is retrieved from the instance of the string, 'Hello'. The program prints 5 to the console, because Hello has five characters in it.

Methods

we use console.log() we’re calling the .log() method on the console object.

Built-in Objects

The .random() method by appending the object name with the dot operator, the name of the method, and opening and closing parentheses. This method returns a random number between 0 and 1. To generate a random number between 0 and 50, we could multiply this result by 50:

Math.random() * 50;

To ensure the answer is a whole number, we can take advantage of another useful Math method called Math.floor(). Math.floor() takes a decimal number, and rounds down to the nearest whole number. 

Math.floor(Math.random() * 50);

Use the .ceil() method to calculate the smallest integer greater than or equal to 43.8.

console.log(Math.ceil(43.8));

What I learned today...

 In this lesson, I learned a lot about how the javaScript language work. At first, I thought Java and JavaScript is the same thing, but after this lesson, I learned that it's totally different, as this language is more direct and easy to learn. However, Java allows us to run it in a virtual machine or browser, javaScript can only be run in browsers.

What i'm doing tomorrow...

 Tomorrow, I will be moving onto the next lesson Variables.