Javascript Data Structure-Array-complete guide
An array is the most common and used data structure in computer programming. This article is part of my data structure series. For a basic introduction please visit the introduction part of this series.
Introduction
For more structured learning documentation. Please take a look at
‘Data-Doc’ online documentation
https://raufr.github.io/datado/Array
Use-cases are more-less the same in all languages. Also, It is a good idea for focusing on concept and structure when learning programming basic, rather than focusing on syntax. Let's begin,
Array
An array is a linear collection of elements, where elements can be accessed via indices, which are usually integers used to compute offsets. In javascript array is a specialized type of object, with the indices being property names that cab ve integers used to represent offsets. But internally indices will convert to string to satisfy javascript object requirement
Creating Array
There are some different ways to create an array from scratch. In the below example first and second is the most common way. The third and fourth represent array constructor (Learn More)
The fifth is a bit different, here we are using a single number which represents the length of the array, and it will be an empty array.
Access Array
The most computation power saving option is using a for-loop. Also using [], is a good option for a single dimensional array.
Another way is using built-in JS functionality like
//Provide index location of an element.indexOf()//Will return last position of string data
lastIndexOf()
Mutate Array
Javascript provides some mutator functions that allow you to modify an array.
.push()
Add an element to the end of an array
Remember! adding data beginning of an array is much harder than adding data to the end of an array.
var arr = [2, 3, 4, 5];
var newEl = 1;
var N = arr.length;
for (var i = N; i >= 0; --i) {
arr[i] = arr[i - 1];
}
arr[0] = newEl;
console.log(arr);//output
[1,2,3,4,5]
.unshift()
Add element at the beginning of an array
.pop()
Remove element from the end of an array
.shift()
Remove element from beginning of an array
.splice()
Adding or removing elements from the middle of an array.
.reverese()
Arranging array elements in reverse.
.sort()
Sort array element, this mutator function worked very well with string.
Remember! sort() will not work properly with numbers, cause the js engine using lexicographical sorting. But!! there is always a way:
Iterate Array
There are two types of iterator functions.
- Non-duplication Iterator functions2
- Duplication iterator functions
Non-duplication Iterator functions:
forEach()
forEach arguments usually a function and run through each element of that array.
every()
Below example pass a function in every() method and depends on the return if..else execute.
some()
This will return boolean depends if some elements exist on the given array.
Duplication iterator functions
map()
The map()function works like the forEach() function.
filter()
Work similar as every() function
Two Dimensional Array
Creating a 2-dimensional array
By default, javascript does not have a two-dimensional array, but we can do this via creating arrays.
We have just scratch the surface of the array in Javascript. The array is the most used and vast data structure in JS, but don't panic, there is nothing but consistent practice and learning will help down the road.
Most of the time, we don't have to use all of the array prototype methods in our day to day life of programming.
I have discussed the most used ones, but feel free to check the below MDN resources for more:
