CODEWITHSUNDEEP
javascript
SumNeuron
SumNeuron

Reputation: 5198

JavaScript: warning against empty types, null, undefined and NaN

I want to make a function warn that serves as a light general error handling function which does the following:

Currently, this is what I have:

function warn(thing, thingString, shouldNotBe, fatal, verbose){
    // default verbose
    if (verbose == undefined) {verbose = true;}
    // default fatal
    if (verbose == undefined) {verbose = false;}

    if (
      thing == shouldNotBe || // test for undefined and null
      (isNaN(shouldNotBe) && shouldNotBe != undefined && isNaN(thing)) // test for NaN
    ) {
      message = thingString + ' is ' + shouldNotBe

      if (fatal) { message = '[FATAL]: ' + message}

      if ( verbose ) { console.warn( message ) }

      if ( fatal ) { return true }
      else { return false }
    }
  }

This lets me do the following in my code:

var myVar
fatal = warn(myVar, 'myVar', undefined, true)
if ( fatal ) {return}

> [Fatal]: myVar is undefined

The problem I am facing is JS's NaN:

NaN === NaN ---> (false)
NaN == NaN ---> (false)
isNaN(NaN)  ---> (true)
isNaN(undefined) ---> (true)
isNaN(null) ---> (false)

So I have to have this ugly conditional (which I could shorten):

(isNaN(shouldNotBe) && shouldNotBe != undefined && isNaN(thing))

to:

So my question is there a better way to approach this problem? The fact that NaN can not be tested by conditional really throws a wrench in this.

Upvotes: 0

Views: 50

Answers (1)

Bergi
Bergi

Reputation: 665276

You can shorten the part isNaN(shouldNotBe) && shouldNotBe != undefined to Number.isNaN(shouldNotBe). You might also be able to use Object.is instead of ==, but then you need special cases for null == undefined and +0 == -0.

Upvotes: 1

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