Javascript array Vs Python list

Introduction

In this article, I will talk about one of the most important and similar data structure in both Javascript and Python.

Javascript array (similar to Python list) is an object that lets you store multiple values in a single variable. For example, an array/list of countries would look like this: ['Nigeria', 'Canada', 'England', 'Mexico', 'China', 'India', 'Kuwait']. While this array/list is made up of only string data type, it can contain multiple data types.

Lets take a look at some commonly used methods when working with array/list in both Javascript and Python.

Creating array/list

There are several ways of creating an array/list in both JS and Py. We will see some of the common ways here.

JS:

let countries0 = ['Nigeria', 'Canada', 'England', 'Mexico', 'China', 'India', 'Kuwait'];

let countries1 = new Array('Nigeria', 'Canada', 'England', 'Mexico', 'China', 'India', 'Kuwait'); 

let countries2 = new Array()
countries1[0] = 'Nigeria';
countries1[1] = 'Canada';
countries1[3] = 'England';

Py:

countries = ['Nigeria', 'Canada', 'England', 'Mexico', 'China', 'India', 'Kuwait']

The list() function in python is used to convert from other types to list.

Adding an element to the end

Lets say, we want to add another country (Germany) to the end of the array/list. In js we use the push() function while in py we use the append() function.

JS:

countries.push('Germany');

Py:

countries.append('Germany')

Adding an element to the beginning

JS:

countries.unshift('USA');

Py:

countries.insert(0, 'USA')

Check if an value is an array or a list

JS:

Array.isArray(countries); // returns true if the object is an array

Py:

type(countries) == list # returns True if the object is a list
isinstance(countries, list)

Removing an element from the end

JS:

countries.pop();

Py:

countries.pop() # by default remove last item
del countries[-1] # -1 means the last index item

Removing an element from the beginning

JS:

countries.shift();

Py:

countries.pop(0)
del countries[0]

Finding an index of an element

JS:

countries.indexOf('India');

Py:

countries.index('India')

Remove item with by specific value

JS:

// JS has no direct function to do this, but it can be manipulated using filter() function as follow;-
var newCountries = countries.filter((value)=>value!='China');

Py:

countries.remove('India')

Check how many items are contained

JS:

countries.length

Py:

len(countries)

Remove all items

JS:

countries.length = 0
countries.splice(0, countries.length) // splice() method changes the contents of an array by removing or replacing existing elements and/or adding new elements in place.

Py:

countries.clear()

Conclusion

This is not in anyway an exhaustive list of operations you can perform with arrays and list in javascript and python respectively. However, with what you have learned here, you can now comfortably work with arrays/lists.

That is it!