JavaScript Arrays

An array is a special variable, which can hold more than one value:
If you have a list of items (a list of car names, for example), storing the 
cars in single variables could look like this:
However, what if you want to loop through the cars and find a specific one? 
And what if you had not 3 cars, but 300?
The solution is an array!
An array can hold many values under a single name, and you can 
access the values by referring to an index number.
Using an array literal is the easiest way to create a JavaScript Array.
Syntax: 
It is a common practice to declare arrays with the const keyword.
Learn more about const with arrays in the chapter: JS Array Const.
Spaces and line breaks are not important. A declaration can span multiple lines:
You can also create an array, and then provide the elements:
The following example also creates an Array, and assigns values to it:
The two examples above do exactly the same.
There is no need to use new Array().
For simplicity, readability and execution speed, use the array literal method.
You access an array element by referring to the index number:
Note: Array indexes start with 0.
[0] is the first element.
[1] is the second element.
This statement changes the value of the first element in cars:
With JavaScript, the full array can be accessed by referring to the array 
name:
Arrays are a special type of objects. The typeof operator in JavaScript returns "object" for 
arrays.
But, JavaScript arrays are best described as arrays.
Arrays use numbers to access its "elements". In this 
example, person[0] 
returns John:
Objects use names to access its "members". In this example, 
person.firstName 
returns John:
JavaScript variables can be objects. Arrays are special kinds of objects.
Because of this, you can have variables of different types in the 
same Array.
You can have objects in an Array. You can have functions in an Array. You can 
have arrays in an Array:
The real strength of JavaScript arrays are the built-in array properties and 
methods:
Array methods are covered in the next chapters.
The length property of an array returns the length of an array (the number of array 
elements).
The length property is always one more than the highest array index.
One way to loop through an array, is using a for loop:
You can also use the Array.forEach() function:
The easiest way to add a new element to an array is using the push() method:
New element can also be added to an array using the length property:
WARNING !

Adding elements with high indexes can create undefined "holes" in an array:
Many programming languages support arrays with named indexes.
Arrays with named indexes are called associative 
arrays (or hashes).
JavaScript does not support arrays with named indexes.
In JavaScript, arrays always use numbered indexes.   
WARNING !!
If you use named indexes, JavaScript will redefine the array to an object.
After that, some array methods and properties will produce incorrect 
results.
In JavaScript, arrays use numbered indexes.   
In JavaScript, objects use named indexes.
Arrays are a special kind of objects, with numbered indexes.
JavaScript does not support associative arrays.
You should use objects when you want the element names to be 
strings (text).
You should use arrays when you want the element names to be
numbers.
JavaScript has a built in array constructor new Array().
But you can safely use [] instead.
These two different statements both create a new empty array named points:
These two different statements both create a new array containing 6 numbers:
The new keyword can produce some unexpected results:
is not the same as:
A common question is: How do I know if a variable is an array?
The problem is that the JavaScript operator typeof returns 
"object":
The typeof operator returns object because a JavaScript array is an 
object. 
To solve this problem ECMAScript 5 (JavaScript 2009) defined a new method Array.isArray():
The instanceof operator returns true if an object is created 
by a given constructor:
For a complete Array reference, go to our:
Complete JavaScript Array Reference.
The reference contains descriptions and examples of all Array 
properties and methods.
Get the value "Volvo" from the cars array.
const cars = ["Saab", "Volvo", "BMW"];
let x = ;

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