JavaScript dynamic data types

-

Default variable type is string ie after declaration the data type is normally string or as most things are objects in JavaScript you can call it that way if you prefer to do so.

ie var name;
condole.log(typeof name) // string

null means a variable is declared but it still has nothing ie its null. null can also be used as a way to unset a variable's value.

Booleans values are true and false.
var on = true;
console.log(typeof on) // Boolean

objects and arrays in JavaScript are of type object ie an array is an object
var matrix = [[0, 1], [1, 0]]
var vector = {"x": 0, "y": 0}

console. log(typeof matrix) // Object
console. log(typeof vector) // Object

functions are also a special datatype
console. log(typeof  function(){}) // function

Comments

Post a Comment

Popular posts from this blog

JavaScript introduction to variables

-
JavaScript is a dynamically typed programming language variables are declared using the following format var `variablename` `value` instead of int integer = 100 In JavaScript a variable can accommodate any typeof value ie a variable can be assigned numbers, strings, functions, and objects. among modern browsers or in "strict mode" variables can be declared in an alternative way using const and let keywords. variable's defined this way's values can not be changed once they have been assigned. ie they are referred to as immutable. var name = "John" var lastname var year = 2020 // var age var male = true console.log( typeof name) // string console.log(typeof lastname) ///undefined console.log(typeof age) // undefined console.log(typeof year) // number console.log(typeof male) // boolean const pi  = 22 / 7 pi = undefined; // sometimes this can raise a typescript error // assignment to constant variable in strict mode console.log(pi) // 3.142...
Read more

Solutions to blocked URLs on Facebook

-
Facebook allows sharing links on it's platform but in order to protect it's users from accessing URLs containing malicious content Facebook on a regular scraps content on shared URLs effectively raising an alarm if content shared goes against Facebook community standards or in short it's content is forbidden on the Facebook platform, Forbidden content may include potentially malicious crafted phishing websites or websites spreading malware among others Facebook may as well ban content flagged spam either reported or flagged by Facebook moderating algorithm "Facebook sheriff" You wouldn't want to find your website 'spam-list handed' you should avoid that There's no way to redeem a website flagged as a blocked website on Facebook except other non viable alternates such as completely changing your domain or using another sub-domain Facebook may as well ban content containing banned URLs in the meta open graph attributes To resolve open-graph sha...
Read more

how to dump a postgresql database using from the terminal

-
PostgreSQL is a relational database management system and arguably the best database management around. postgreSQL comes with utilities used to manipulate databases from the terminal "psql" being the most popular utility I'm sure you've read somewhere or used "psql" dumping "backing" databases is done using PostgreSQL's pg_dump utility In your terminal type; pg_dump <database name> > <output> For instance to backup a database named "books" to a file named "books.sql" do; pg_dump "books" > books.sql How to exclude database data from backups To exclude database data from your output file you should include "-s" flag in your command pg_dump -s "books" > books.sql
Read more

How to set content disposition headers for express nodejs apps

-
Image
In express nodejs apps you can force the user agent "browser" to rather download content instead of displaying or attempting to render given content within the browser. In this example assuming you're using express.static to serve content pass an Object as second argument to express.static function An Object with configuration parameters; const config = { setHeaders: res => res.set('Content-disposition',  'attachment') } In your code replace "path/to/media/" with the path pointing to the static content. app.use('/media/', express.static('path/to/media/', config)) To test try accessing content at /media/*
Read more

How to get user's ip address in JavaScript

-
An IP address is a unique numerical label given to a computer when connected to a network; ipify.org is a free service that retrieves IP addresses in JSON format fetch('https://api.ipify. org ?format=json') .then(response => response.json()) .then(response => console.log(JSON.stringify(response))) // response {"ip":"--.---.---.---"} In nodejs you can use a package node-fetch Install it by typing; npm i node-fetch Or using curl, in your terminal type; curl 'https://api6.ipify.org?format=json' // response {"ip":"--.---.---.---"}
Read more