Intro to Javascript

Javascript was created in 10 days in May 1995 by Brendan Eich while working at Netscape. It was named Javascript because Java was a very popular language at the time.

Numbers

Numbers in Javascript are 64-bit floating point. There are no integers.

var numbo = 10000000000000000;

Advantages - no overflows or floating-point errors. high precision.

Disadvantages - performance, memory.

Strings

Strings are defined inside of a single or double quote. (Pick one. Don’t mix.)

var str = "hi i'm a string";

Basic operations are + for concatenation and .length to get the length of the string.

Other useful operators are trim, substr, charAt, split, match, and many many more.

Arrays

Arrays can be defined in a couple ways.

var arr = new Array(100);
// or
var arrTwo = [];

Access arrays using []

var firstElement = arr[0];

Arrays have a lot of useful methods like push, pop, shift, sort, and many more.

What would you hold in an array?

Object Literals / Maps / Dictionaries

Defining an Object:

var objTwo = {};

Accessing data in the object

var data = obj.parameter;
var sameData = obj["parameter"];

Self referential object.

var obj.obj = obj;

Pointers

Everyone is always talking about them. What are they?

var a = {
	"data" : "something"
};
var b = a;
b.data = "something else";
a.data; // "something else"

What would you hold in a dictionary?

Functions

Can be defined in a few ways.

var funky = function(parameter){
	//body
};
// or
function funkyToo(parameter){
	//body
}

And later invoked with ()

funky("argument");

It can just be passed around like any other variable.

console.log(funky); 
// prints:
function(parameter){
	//body
};

Anonymous and immediately invoked functions

(function(){
	console.log("i was immediately invoked");
})();
//is subtly, but importantly different from
console.log("i was immediately invoked");

Scope

functions create scope. Scope allows an inside function to see all of it’s parents, but not a parent scope to see anything about the children.

function scopes(){
	var you = "you";
	(function(){
		var me = "me";
		console.log("i can see " + you);
	})();
	console.log(you + "can't see " + me);
}
//this throws an error that 'me' is undefined.

SERVERS

What do servers do?

• Client/Server communication
• AJAX
• Store things
• Synchronize multiple pages

Spinning up a simple file server

If you have python installed, in the terminal type:

python -m SimpleHTTPServer

or if you have node.js and http-server installed:

to install http-server: npm install -g http-server

http-server

Then you can visit the page through your local IP address:

http://localhost:8000/

(Note that the port number of your server might be different than 8000)

ctrl + c to kill the server