Data Types

Strings

• Strings can consist of letters and other characters

• They are surrounded by either double quotes or single quotes

• Concatenation allows you to combine strings

// declare a variable called color and store a string 

var color = "green";

String Methods

• Javascript has some built-in methods that allow developers to work with strings

• For example: if you wanted to know how many characters were in a string, you would use the .length method

• Here are some example of other methods you can use on strings

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Numbers

• Used for tasks involving counting or calculating sums

• Whole numbers (integers) or decimals (floats)

• Numbers can be negative or positive

• Numbers do not have quotes around them

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Converting Strings to Numbers

• Sometimes you will find yourself in a position where you need to convert a string to a number

• This happens when you attempt to read numeric values from html (html displays everything as a string)

• Use the parseInt() or parseFloat() methods to accomplish this

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Booleans

• Can only have a value of true or false

• true/false are special keywords in javascript and do not have quotes around them

// declare a variable called isOn and assign a value of true
var isOn = true;

// declare a variable called isWarm
var isWarm;

// assign a value of false to isWarm
isWarm = false;

• Booleans are useful for helping our programs make decisions (when used with conditionals, comparison & logical operators)

• Booleans also helps a program known when it should stop/start looping

Arrays

• Used to when you are working with a list of values that are related to each otehr

• Use square brackets to create an array

• Values in an array are separated by commas

Creating an Array

• We can store variables just like any other data type

• You can create that doesn’t initially contain any values, this is called an empty array

• An array can also be created with initial values

• Square brackets are a means of identifying if a variable is an array

// declare a variable as an empty array

var numbers = [];

// or you can declare an array with initial values

var streets = ['Broadway', 'Houston', 'Grand'];

Values in an Array

• Values in an array are accessed as if they are in a numbered list

• Arrays are zero based meaning the 1st “value” in an array is at position (index) 0, the 2nd element is at position 1, and so on

• You access the value of an element in the array by passing the index of the item in square brackets

var streets = ['Broadway', 'Houston', 'Grand'];

// access the 2nd street listed in the array which is at index 1
var streetTwo = streets[1];

Accessing in an Array

• You can access a value of an array by referencing its index (i.e. its order within the array)

// declare a variable called chipmunks and use it to store
// an array of names
var chipmunks = ["Alvin", "Simon", "Theodore"];

// reference the first value in the array
// here we pass in a zero, since that represents the first
// element (value) in an array

var bandMember = chipmunks[0];

// the value stored in bandMember is "Alvin"

Changing Values in an Array

• You can change a value in an array by referencing the value and then changing the value using an = (equal sign)

// declare a variable called newEditionMembers and use it to store
// an array of names

var newEditionMembers = ["Ricky Bell", "Michael Bivins", "Bobby Brown", "Ronnie DeVoe", "Ralph Tresvant"]

// We are going replace Bobby Brown with Johnny Gill 
// by referencing the 3rd element of the array by using index 2
// and then use assignment (just an equal sign) to change
// the value to Johnny Gill

newEditionMembers[2] = "Johnny Gill";

Array Examples

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Objects

• Objects are used to represent real world objects in programming

• Within an object, variables are known as properties and functions are known as methods

• Curly braces are a means of identifying if a variable is an object

// create an object that represents a dog

var myDog = {
	name: "Fido",
	age: 4,
	speak: function() {
     console.log('Woof woof');
	} 
}

• In the example above, we created an object and stored it in a variable called myDog

• This object has 2 properties (name and age) and 1 method (speak)

This of method as **actions** that our objects can take

Accessing Properties and Methods of Objects

• Properties and values can be assigned and read using Dot notation

var myDog = { 
  name: "Fido",
  age: 4,
  speak: function() {
     console.log('Woof woof');
	} 
}

// store myDog's name in a variable called dogName
var dogName = myDog.name;

// call the speak method of myDog 
myDog.speak();

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Updating Object properties using dot notation

• Object properties can be updated, added or deleted

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