Table of Contents
Introduction
A JavaScript Array is used to store multiple values in a single variable.
Example: Array of single digit numbers
myArray = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
Creating an Array
An array can be created using following two ways:
- Using array literal
var myArray = [ ];
- Using JavaScript Keyword new
var myArray = new Array( );
Access an element of an Array
An element of an array can be accessed by referring its position also known as index number.
Suppose, we have an array myArray of different computer languages.
myArray = [“C”, “C++”, “JavaScript”, “ABAP”, “Java”];
The index of an array starts from 0. Therefore, [0] will be the first element and [1] will be the second element.
We can access any of the element by referring its index as shown below:
myElement = myArray[2];
Output: “JavaScript”
Looping Array Elements
To Loop each of the element, we can use a for loop as shown below:
Example: In given example we will check if the array of devices has laptop or not.
var device = [“mobile”, “computer”, “laptop”, “earphone”]
var dLength = device.length;
for (i = 0; i < dLength; i++)
{
If (device[i] = “laptop”)
console.log(“Yes, array has laptop as a device!”);
}
Operations on JavaScript Array
We can perform following operations on an Array:
In given examples, we will perform operations on an array numbers = [1,2,3,4];
| Operation | Description | Example |
| pop() | This method removes the last element of an array. | numbers.pop(); Output: [1,2,3] |
| push() | This method adds a new element in the end. | numbers.push(5); Output: [1,2,3,4,5] |
| length | This is a property of array and it returns the length of an array. | numbers.length; Output: 4 |
| shift() | This method removes the first element of an array and shifts all the other elements to the lower index. | numbers.shift(); Output: [2,3,4] |
| unshift() | This method adds a new element at the beginning. | numbers.unshift(0); Output: [0,1,2,3,4] |
| forEach() | This method calls a function once for each array element. | numbers.forEach(function(num){ if(num == 2) console.log(“2 is there”); }); Output: 2 is there |
| toString() | This method converts an array to a string of array values separated by comma. | number.toString(); Output: 1,2,3,4 |
| delete | This method converts an element to undefined. It is recommended to pop() or shift() to remove an element in place of delete. | delete numbers[0]; console.log(numbers[0]); Output: undefined |
| splice(a,b) | This method is used to delete and insert new items. Here a is the index where we want to insert/delete items and b is the number of elements that will be deleted. Anything added after these parameters i.e. a and b will be inserted at the index a. | 1. Deleting items numbers.splice(0,1); console.log(numbers); Output: [2,3,4] 2. Adding items numbers.splice(0,1,-1); console.log(numbers); Output: [-1,2,3,4] |
| slice(a,b) | This method slices out a part of an array into a new array. Here, a is the index from where the slice begins and b is the index where it ends, excluding b. If there is no ending index i.e. b, then all the rest elements beginning from a is sliced. | var newSet = numbers.slice(1,3) console.log(newSet); Output: [2,3] |
| concat() | This method concatenates two arrays into a new array. | var numbers2 = [5,6,7,8] var mergeSet = numbers.concat(numbers2); console.log(mergeSet); Output: [1, 2, 3, 4, 5,6,7,8] |
| sort() | This method sorts an array alphabetically/numerically in ascending order. | var set = [1,2,3,4,0]; set.sort(); console.log(set); Output: [0,1,2,3,4] |
| reverse() | This method reverses the elements of an array. This method can be used to sort an array in descending order which is already sorted in ascending order. | numbers.reverse(); console.log(numbers); Output: [4,3,2,1] |
| indexOf() | This method searches for an element value and returns its position into a new variable. | var a = numbers.indexOf(1); console.log(a); Output: 0 |
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