Arrays in Javascript
Hello folks!, I'm Miheer this is a simple guide for ["Arrays", "in", "javascript"].
As of now, you are reading this article, which means you have knowledge of basic datatypes in javascript.
Like Primitive and Non-primitive.
Primitive datatypes such as Number, Boolean, Strings, Undefined, Null, BigInt, Symbol.
and Non-primitive such as Arrays & Objects. Don't worry about objects right now we will look later on them.
So, the question is why do we need arrays? after all, we have seven different datatypes.
Arrays can store a list of different datatypes.
Arrays handle a large amount of data under a single variable.
We can access all values in an array by a single variable name and manipulate it.
Now, we know why arrays are so important in a programming language ( Javascript ).
What is an array?
An array is a Data Structure or we can say a container that holds values of single data types as well as multiple data types.
Let's start with the Arrays :
Declaration
1. Using bracket notation :
To create an array you can simply add a const and set is equal to [] brackets. Which will create an empty array.
const array = [];
// you can add a values in it like
const numArray = [1, 3, 5, 7];
// try
console.log(numArray);
// output : [1, 3, 5, 7]
2. Using Object constructor:
To create an array using the object constructor add const and set a value to new Array(). It will create an empty array.
const arr = new Array();
// will create empty array, Check using console.log();
Now if we add values in-between () like so Array(1,2,3).
const arr = new Array(1, 2, 3);
// will get, [1, 2, 3]
If we give a single value to a Array(7). It will create an empty array of length 7.
const arr = new Array(7);
// [ <7 empty items> ]
// we can fill the items using fill();
const arr = new Array(7).fill(1);
// output : [1, 1, 1, 1, 1, 1, 1]
There is a most important and useful property .length. which gives the length of an array or how many elements are stored inside of an array. We can also set the length of an array using this property arr.length = 10, but I don't recommend doing that.
// we can access it using .length
console.log(arr.length);
// 7
How we can get and set the array values :
We can get the values using [] around our variable like arr[index], and also set using same arr[index] = newValue.
const arr = [1, 2, 3, 4];
console.log(arr[1]);
// output : 2, Because at index 1 the value in array is 2.
arr[0] = 7;
console.log(arr);
// output : [7, 2, 3, 4];
The most important thing to remember the index of an array starts from 0.
Array methods
Now, we will look into array methods which can be very helpful while working with arrays.
A List of numbers or strings is the best example of an array. array provides methods for adding/removing items from it. We have these first four methods to work with an array, there are a lot more and important as well but these are the basic ones. Which are push(), pop(), shift() & unshift().
We will look into them one by one.
IMPORTANT: This methods manipulate the original array only and do not return a new one.
The first one is the push(...items) method. Which adds a new item to the end of an array.
const arr = ["first","second","third"];
arr.push("fourth");
console.log(arr);
// output : ["first", "second", "third", "fourth"]
The next one is pop() which remove item from the end.
const arr = ["first","second","third"];
arr.pop();
console.log(arr);
// output : ["first", "second"]
Similar to this two we have shift() & unshift(..items). Which does the same thing but from the beginning.
const arr = ["first","second","third"];
arr.unshift("fourth");
console.log(arr);
// output : ["fourth", "first", "second", "third"]
const arr = ["fourth", "first", "second", "third"];
arr.shift();
console.log(arr);
// output : ["first", "second", "third"]
Okay, that's it for this post there are more array methods, we will look at them in the next part of this blogpost. Hope you learned something from this post. Thank you.
Always pass on what you have learned - Yoda.