As we learned, a variable can hold only one value, for example, var i = 1, we can assign only one literal value to i. We cannot assign multiple literal values to a variable i. To overcome this problem, JavaScript provides an array.

There is a special type of variable called an array, which can store multiple values using special syntax. Every value is associated with numeric index starting with 0.

There are 3 ways to construct array in JavaScript

1. By array literal
2. By creating instance of Array directly (using new keyword)
3. By using an Array constructor (using new keyword)

1) JavaScript array literal:

The syntax of creating array using array literal is given below:

var arrayname=[value1,value2.....valueN];

example:

<script>  
var emp=["Sonoo","Vimal","Ratan"];  
for (i=0;i<emp.length;i++){  
document.write(emp[i] + "<br/>");  
}  
</script>

Output:

Sonoo
Vimal
Ratan

2-JavaScript Array directly (new keyword):

syntax:

var arrayname=new Array();

Here, new keyword is used to create instance of array. Example:

<script>  
var i;  
var emp = new Array();  
emp[0] = "Arun";  
emp[1] = "Varun";  
emp[2] = "John";  

for (i=0;i<emp.length;i++){  
document.write(emp[i] + "<br>");  
}  
</script>

Output:

Arun
Varun
John

3) JavaScript array constructor (new keyword):

const array2 = new Array("Saab", "Volvo", "BMW");

Example:

<script>  
var emp=new Array("Jai","Vijay","Smith");  
for (i=0;i<emp.length;i++){  
document.write(emp[i] + "<br>");  
}  
</script>

Output:

Jai
Vijay
Smith

JavaScript Array Methods:

• concat() :It returns a new array object that contains two or more merged arrays.
• copywithin() :It copies the part of the given array with its own elements and returns the modified array.
• entries() :It creates an iterator object and a loop that iterates over each key/value pair.
• every() :It determines whether all the elements of an array are satisfying the provided function conditions.
• flat() :It creates a new array carrying sub-array elements concatenated recursively till the specified depth.
• flatMap() :It maps all array elements via mapping function, then flattens the result into a new array.
• fill() :It fills elements into an array with static values.
• from() :It creates a new array carrying the exact copy of another array element.
• filter() :It returns the new array containing the elements that pass the provided function conditions.
• find() :It returns the value of the first element in the given array that satisfies the specified condition.
• findIndex() :It returns the index value of the first element in the given array that satisfies the specified condition.
• forEach() :It invokes the provided function once for each element of an array.
• includes() :It checks whether the given array contains the specified element.
• indexOf() :It searches the specified element in the given array and returns the index of the first match.
• isArray() :It tests if the passed value ia an array.
• join() :It joins the elements of an array as a string.
• keys() :It creates an iterator object that contains only the keys of the array, then loops through these keys.
• lastIndexOf() :It searches the specified element in the given array and returns the index of the last match.
• map() :It calls the specified function for every array element and returns the new array
• of() :It creates a new array from a variable number of arguments, holding any type of argument.
• pop() :It removes and returns the last element of an array.
• push() :It adds one or more elements to the end of an array.
• reverse() :It reverses the elements of given array.
• reduce(function, initial) :It executes a provided function for each value from left to right and reduces the array to a single value.
• reduceRight() :It executes a provided function for each value from right to left and reduces the array to a single value.
• some() :It determines if any element of the array passes the test of the implemented function.
• shift() :It removes and returns the first element of an array.
• slice() :It returns a new array containing the copy of the part of the given array.
• sort() :It returns the element of the given array in a sorted order.
• splice() :It add/remove elements to/from the given array.
• toLocaleString() :It returns a string containing all the elements of a specified array.
• toString() :It converts the elements of a specified array into string form, without affecting the original array.
• unshift() :It adds one or more elements in the beginning of the given array.

• values() :It creates a new iterator object carrying values for each index in the array.

  Points to Remember :

• An array is a special type of variable that stores multiple values using a special syntax.
• An array can be created using array literal or Array constructor syntax.
• Array literal syntax: var stringArray = ["one", "two", "three"];
• Array constructor syntax:var numericArray = new Array(3);
• A single array can store values of different data types.
• An array elements (values) can be accessed using zero based index (key). e.g. array[0].
• An array index must be numeric.
• Array includes length property and various methods to operate on array objects.