DEV Community: Janaka Dissanayake

Is NAN Not a Number?

Janaka Dissanayake — Wed, 13 Nov 2019 12:53:39 +0000

Recently Javascript became my main development language so I have to solve complex problems using javascript, one of the challenging tasks was in Numeric operation how to represent the absence of a numeric value, do we use

0           // 0 has a specific value 
undefined   // it is not numeric
null        // it is an object
false       // boolean type
-1          // another specific value

In IEEE spec give special bit pattern or values call NAN, it is called invalid number

typeof NaN  // "number"

So if we use numeric operation in a function we need to get a numeric answer

const ageCompare = (age,newAge) => { 
  return Number(age) - Number(newAge)
}

const result = ageCompare(10,2)     // 8
const result = ageCompare(10,"n/a") // NaN
const result = ageCompare("myAge","n/a") // NaN

Number.isNaN(result) ... // true

*** NAN is the only value that not equal to each other

NAN===NAN  // false

Please refer following a link that gives a good explanation by Kyle Simpson
https://frontendmasters.com/courses/deep-javascript-v3/nan-isnan/

What is Constructor in Javascript

Janaka Dissanayake — Mon, 05 Nov 2018 06:15:44 +0000

In JS world there is a term called the constructor, people like me who have C#/Java background has a lot of confusion when it implements this in a real application. So I have done a small research and came with the following understanding

function jsObject(name){ this.name = name };
// call function
let obj = jsObject("myName");
obj.name;

// VM603:1 Uncaught TypeError: Cannot read property 'name' of undefined
// at <anonymous>:1:3

Les't fix this

function jsObject(name){ 
   var myObj = {};
   myObj.name = name;
   return myObj;
};

// call function
let obj = jsObject("myName");
obj.name;

// --> myname

works fine, so that is, NO javascript give some cool feature


// call function
let obj =  new jsObject("myName");
obj.name;
// --> myname

what happened, yes javascript gives some cool stuff to developers.it adds following line at runtime when it is called with new.


function jsObject(name){ 
   // var this = {};-> add at run time 
   this.name = name;
   // return this; -> add at run time 
};

Now I know constructor function, but feel free to add your comments

Hi, I'm Janaka Dissanayake

Janaka Dissanayake — Thu, 22 Jun 2017 00:37:21 +0000

I have been coding for 10 years.

You can find me on GitHub as jdissan

I live in Melbourne.

I mostly program in these languages: C#, Javascript, Elm.

I am currently learning more about Serverless Architecture.

Nice to meet you.