var arrayExample = [7,11,6,55,98,45,16,96,46];

Creating an Array (Declaring)

var cars = [];   //This is an empty array

OR WITH VALUES

var cars = ["Saab", "Volvo", "BMW"]; 

Updating specific values in an array. We use its index number to reference

cars[0] = "Opel"; 

Now cars =["Opel", "Volvo", "BMW"]; 

Getting values from an array - if we know the index

["Opel", "Volvo", "BMW"]; 

var x = cars[1];

x = "Volvo"

Adding new items to the end of the array

• We use push()

cars.push("Toyota")

["Opel", "Volvo", "BMW", "Toyota"]; 

Deleting an Item from array using splice

cars.splice(2,1) // go to index 2 and remove 1 item

["Opel", "Volvo",  "Toyota"]; 

Handy Array Methods and Properties

var x = cars.length;   // The length property returns the number of elements

var y = cars.sort();   // The sort() method sorts arrays by the value inside each index

Array Basics Summary

//create a array of values

var vals = [1,2,3,4,5];

var vals = [];  //empty array

//print array to console log

console.log(vals);

//access an elemement in an array at index 3

console.log(vals[3]);

//add a new item/value to an array

vals.push(10); //adds value 10 to the array called vals

console.log(vals);

//delete last item from array

vals.pop();

console.log(vals);

//delete a specific item from array splice(index, how many)

vals.splice(0,1);

//first value is index start and second value is how many to delete = keep as 1

//loop through an array from first to last index using a for loop

//length returns the number of items in an array

for(var i=0; i<vals.length;i++){

  console.log(vals[i]);

}

Objects can store multiple values about one object. An example is a person object. People have lots of properties like first, last names, age, DOB.

 We declare a single object like this using curly brackets

var person = {firstName:"John", lastName:"Doe", age:46}; 

• We can access the attributes of each object like this:

person.lastName;  OR  person["lastName"]; 

Storing objects in an array to be able to store lots of objects

var people = [

{first: "ted", last: "smith" , age: 20}, //index 0

{first: "Sam", last: "apple" , age: 90} //index 1

];

Accessing object from an array list

people[0].first //would print "ted"

console.log("Hello " + people[0].first + " " + people[0].last)     //output = Hello ted smith

Object Methods

These are declared inside the object declaration. The this command refers to the current object attribute.

fullName : function() {

        return this.firstName + " " + this.lastName;

    } 

The method can be executed against an object by using the following notation:

objectName.methodName() 

Objects stored in arrays

Array of objects - obects start and end with curly braces {} Properties are declared with a colon:

var cars = [

{car:"Ford",year:1999},

{car:"Holden",year:2009}

]

//access object in an array using the dot notation to access the property

console.log(cars[0].car);

console.log(cars[0].year);

//add an object to an array

cars.push({car:"Subaru",year:2020});

console.log(cars[2].car);

console.log(cars[2].year);

Array of Objects Sorting

Source: https://www.javascripttutorial.net/array/javascript-sort-an-array-of-objects/#:~:text=To%20sort%20an%20array%20of%20objects%2C%20you%20use%20the%20sort,determines%20the%20order%20of%20objects.

Sort an array of objects by a NUMBER property

employees.sort((a, b) => {

    return a.age - b.age;

}); 

Sort an array of objects by a STRING property. NOTE: You must convert to lowercase as lowercase characters are lower then uppercase.

employees.sort((a, b) => {

    let fa = a.firstName.toLowerCase(),

        fb = b.firstName.toLowerCase();

    if (fa < fb) {

        return -1;

    }

    if (fa > fb) {

        return 1;

    }

    return 0;

}); 

Sort an array of objects by date

employees.sort((a, b) => {

    let da = new Date(a.joinedDate),

        db = new Date(b.joinedDate);

    return da - db;

}); 

Simple way to output objects

employees.forEach((e) => {

    console.log(`${e.firstName} ${e.lastName} ${e.joinedDate}`);

});