Introduction to Arrays in JavaScript
As we know objects allow us to store keyed collections of values. But sometimes we need an ordered collection, where we have to store 1st, 2nd, 3rd element and many more. For instance, consider we need to store a list of something: users’ data, goods data, and many more. It is not appropriate to use an object here, because it provides no methods to manage the order of elements. Objects are not created for such use. There exists a special data structure called Array, to store ordered collections. Arrays in JavaScript enables multiple values to be stored in a single variable. It stores the same kind of element collection sequential fixed-size.
Arrays in JavaScript are used to store an information set, but it is often more helpful for storing a set of variables of the same type. An array is a single variable in JavaScript that is used to store various elements. When we want to store a list of elements and access them through a single variable, it is often used. Unlike many other languages where an array is a various variable reference, there is a single variable in the JavaScript array that stores various elements. The object Arrays in JavaScript are a global object used in array building; which is high-level, list-like objects.
How does the array work in JavaScript?
Arrays in JavaScript are a way to store elements in a single variable in memory. By its index, the elements can be accessed in the array. The array index starts with 0. Javascript arrays are zero-based, meaning the first element index is 0. This is very important because it means that an offset of one unit will always exist: the first element will have an index of 0, and the second element will have an index of 1, and so on.
How to create arrays in JavaScript (example)?
The object Array allows you to store various values in one variable. It stores a sequential fixed-size collection of the same type of elements. An array is used to store a collection set, but it is often more helpful to consider an array as a set of the same type of variables. The literal notation array makes it simple to create arrays in JavaScript. It comprises of two square brackets that wrap optional, comma-separated array elements. Number, string, boolean, null, undefined, object, function, regular expression, and other structures can be any type of array elements.
The array can be created in JavaScript as given below
var country = ["India", "England", "Srilanka"];
In the above creation, you are initializing an array and it has been created with values “India”, “England”, and “Srilanka”. The index of “India”, “England”, and “Srilanka” is 0, 1 and 2 respectively. You can add extra elements to the country array, then you can do it as shown below
country[3] = "New Zealand";
country[4] = "Australia"
var country = new Array("India", "England", "Srilanka");
OR
var country = new Array();
country[0] = "India";
country[1] = "England";
country[2] = "Srilanka";
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Example
<html>
<head>
<title>JavaScript Creating Array</title>
</head>
<body>
<p id="myarray"></p>
<script>
var my_array=["England","Australia","India"];
document.getElementById("myarray").innerHTML = my_array;
</script>
</body>
</html>
Output
Types of arrays in JavaScript (Explain each type with example)
Below are the different types of arrays in javascript as follows:
-
Array Literal
The array can be created with an array literal by using below syntax
var arrayname=[value1,value2.....valuen];
Consider the simple example of creating an array in JavaScript by using Array Literal
<html>
<head>
<title>Array Literal</title>
</head>
<body>
<script>
var country=["India","Australia","England"];
for (i=0;i<country.length;i++){
document.write(country[i] + "<br/>");
}
</script>
</body>
</html>
Output:
-
Array Directly
The array can be created with array directly by using the new keyword as shown below in the syntax
var arrayname=new Array();
Below an example of creating an array in JavaScript by using Array Directly with the help of the new keyword
<html>
<head>
<title>Array Directly</title>
</head>
<body>
<script>
var num;
var country = new Array();
country[0] = "India";
country[1] = "Australia";
country[2] = "England";
for (num=0;num<emp.length;num++){
document.write(emp[num] + "<br>");
}
</script>
</body>
</html>
Output:
-
Array Constructor
The array instance can be created by passing arguments in a constructor. The following example creates an array in JavaScript by using Array Constructor with the help of the new keyword
<html>
<head>
<title>Array Constructor</title>
</head>
<body>
<script>
var num;
var country = new Array();
country[0] = "India";
country[1] = "Australia";
country[2] = "England";
for (num=0;num<country.length;num++){
document.write(country[num] + "<br>");
}
</script>
</body>
</html>
Output
Explain array methods in JavaScript
Below are the array methods in JavaScript as follows
1. concat() method
You can create a new array with a combination of two or more arrays with the help of the concat() method.
Syntax
array.concat(val1, val2, ..., valN);
Example
<html>
<head>
<title>JavaScript Array Method</title>
</head>
<body>
<script>
var chars = ["A", "B", "C"];
var num = [10, 20, 30];
var concat_res = chars.concat(num);
document.write("Concatenated Result : " + concat_res );
</script>
</body>
</html>
Output
2. every()
every() method checks whether given elements are true or false in an array as provided in the condition. It returns true if condition matches given condition otherwise returns false.
Syntax
Array.every(callback,thisArg)
Where callback is a condition to test the function and thisArg is an optional parameter used when executing the callback.
Example
<html>
<head>
<title>JavaScript Array Method</title>
</head>
<body>
<script>
var vals=[150,400,450,375,200];
function check_num(value)
{
return value>100;
}
document.writeln(vals.every(check_num));
</script>
</body>
</html>
Output
3. fill()
The fill() method is used to fill the specified static values by modifying original values in the given array.
Syntax
array.fill(value)
Example
<html>
<head>
<title>JavaScript Array Method</title>
</head>
<body>
<script>
var my_array=["England","Australia","India"];
var array_result=my_array.fill("EDUCBA");
document.writeln(my_array);
</script>
</body>
</html>
Output
4. filter()
The filter() method is used to filter the array elements based on the given condition.
Syntax
array.filter(callback, thisArg)
Example
<html>
<head>
<title>JavaScript Array Method</title>
</head>
<body>
<script>
var vals=[150,200,345,375,125];
function check_num(value)
{
return value>150;
}document.writeln(vals.filter(check_num));
</script>
</body>
</html>
Output
5. forEach()
The forEach() method is used to invoke the function for each array element.
Syntax
array.forEach(callback, thisArg)
Example
<html>
<head>
<title>JavaScript Array Method</title>
</head>
<body>
<script>
var my_array = ['India', 'Srilanka', 'England'];
my_array.forEach(function(fetch) {
document.writeln(fetch);
});
</script>
</body>
</html>
Output
6. includes()
The includes() method is used to check whether the given element is included in the array or not. If the element is included in an array, then it returns true otherwise returns false.
Syntax
array.includes(element) //where “element” is a value which is to be searched in the array
Example
<html>
<head>
<title>JavaScript Array Method</title>
</head>
<body>
<script>
var my_array=["Sachin","Dhoni","Kohli","Rohit","Dhawan"]
var array_result=my_array.includes("Sachin");
document.writeln(array_result);
</script>
</body>
</html>
Output
7. join()
The join() method is used to combine the array elements into the string and provides a new string.
Syntax
array.join(separator)
Example
<html>
<head>
<title>JavaScript Array Method</title>
</head>
<body>
<script>
var my_array=['India', 'Srilanka', 'England']
var array_result=my_array.join('-')
document.write(array_result);
</script>
</body>
</html>
Output
8. pop()
The pop() method is used to extract the last element of the given array.
Syntax
array.pop(operator)
Example
<html>
<head>
<title>JavaScript Array Method</title>
</head>
<body>
<script>
var my_array=["England","Australia","India"];
document.writeln("Real array elements: "+my_array+"<br>");
document.writeln("Extracted element of array: "+my_array.pop()+"<br>");
document.writeln("Remaining elements of array: "+ my_array);
</script>
</body>
</html>
Output
9. push()
The push() method is used to add the element to the end of the array.
Syntax
array.push()
Example
<html>
<head>
<title>JavaScript Array Method</title>
</head>
<body>
<script>
var my_array=["England","Australia","India"];
my_array.push("Srilanka");
document.writeln(my_array);
</script>
</body>
</html>
Output
10. reverse()
The reverse() method is used to reverse the sequence of the given array of elements. The last element will become the first and the first element will become last.
Syntax
array.reverse()
Example
<html>
<head>
<title>JavaScript Array Method</title>
</head>
<body>
<script>
var my_array=["England","Australia","India"];
var reverse_val=arr.reverse();
document.writeln(reverse_val);
</script>
</body>
</html>
Output
11. shift()
The shift() method is used to return the first element of an array.
Syntax
array.shift()
Example
<html>
<head>
<title>JavaScript Array Method</title>
</head>
<body>
<script>
var my_array=["Dhoni","Sachin","Kohli","Rohit","Dhawan"];
var array_result=my_array.shift();
document.writeln(array_result);
</script>
</body>
</html>
Output
12. slice()
The slice() method is used to display part of the given array elements without changing the original array.
Syntax
array.slice(start,end)
Example
<html>
<head>
<title>JavaScript Array Method</title>
</head>
<body>
<script>
var my_array=["Dhoni","Sachin","Kohli","Rohit","Dhawan"];
var array_result=my_array.slice(2,3);
document.writeln(array_result);
</script>
</body>
</html>
Output
13. sort()
The sort() method is used to display the array elements in ascending order.
Syntax
array.sort()
Example
<html>
<head>
<title>JavaScript Array Method</title>
</head>
<body>
<script>
var my_array=["Dhoni","Sachin","Kohli","Rohit","Dhawan"];
var array_result=my_array.sort();
document.writeln(array_result);
</script>
</body>
</html>
Output
14. unshift()
The unshift() method is used to add elements at the beginning of the array.
Syntax
array.unshift(“element”)
Example
<html>
<head>
<title>JavaScript Array Method</title>
</head>
<body>
<script>
var my_array=["Dhoni","Sachin","Rohit","Dhawan"];
var array_result=my_array.unshift("Kohli");
document.writeln(my_array);
</script>
</body>
</html>
Output
15. indexOf()
The indexOf() method is used to search the position of an element in a given array.
Syntax
array.indexOf(“element”)
Example
<html>
<head>
<title>JavaScript Array Method</title>
</head>
<body>
<script>
var my_array=["Dhoni","Sachin","Rohit","Dhawan"];
var array_result=my_array.indexOf("Rohit");
document.writeln(array_result);
</script>
</body>
</html>
Output
Conclusion
As discussed until now, an array is a special kind of object for storing and managing data elements. An array is an object, that provides a group of elements and useful for storing a large amount of data of the same type. The properties and methods of array objects help developers to handle arrays easily. As a global object, the JavaScript Array can be used in the construction of arrays that are high-level.
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