super()

Hey, am i using super() correctly in this case? I had a bit a trouble understanding the functionality.

class Animal {
  constructor(species) {
    this.species = species
  }
  get Species() {
    return this.species
  }
}

class Spider extends Animal {
  constructor(species, type) {
    super(species)
    this.type = type
  }
  get SpeciesReason() {
    return `I'm an ${this.species} because I have 8 legs.`
  }
}

let spider = new Spider("Arachnid", "House Spider");

class Animal {
  constructor(species) {
    this.species = species
  }
  get Species() {
    return this.species
  }
}

class Spider extends Animal {
  constructor(species, type) {
    super(species)
    this.type = type
  }
  get SpeciesReason() {
    return `I'm an ${this.species} because I have 8 legs.`
  }
}

let spider = new Spider("Arachnid", "House Spider");

I've played around with it and found the following which makes me think that i'm doing everything right as it works, but i might be wrong. 1) If i don't include super() and species in the constructor args for the Spider class, since it has it's own constructor it throws an error saying must call super constructor before using 'this' in derived class constructor as i'm trying to use this.species. 2) If i don't include species in the constructor args but have a super(species) it throws an error saying species isn't defined. 3) If i include species in the constructor args but don't include super(species) it throws an error saying must call super constructor before using 'this' in derived class constructor. I'd appreciate any insight. Thanks in advance.

33 Replies

ἔρως•2mo ago

you didn't define the public property species in the class Animal you also didn't define type in Spider calling super is mandatory - no way around it unless EVERYTHING is static

snxxwyyOP•2mo ago

i know, i was checking if i was using it correctly?

ἔρως•2mo ago

which is not what you want you are, yes

snxxwyyOP•2mo ago

also i'm confused about the first two things you said, are you saying those in reference to the errors, or are they just general things i'm not doing? oh cool, glad i got that down

ἔρως•2mo ago

both

snxxwyyOP•2mo ago

oh so i need to do this?

class Animal {
  species;

  constructor(species) {
    this.species = species
  }
  get Species() {
    return this.species
  }
}

class Animal {
  species;

  constructor(species) {
    this.species = species
  }
  get Species() {
    return this.species
  }
}

and then the same for type in Spider?

ἔρως•2mo ago

snxxwyyOP•2mo ago

oh?

ἔρως•2mo ago

inside the class

snxxwyyOP•2mo ago

oh yeah just changed that haha realised just then okay so if it's inside the class, then like that?

ἔρως•2mo ago

yes, like that

snxxwyyOP•2mo ago

okay cool, thanks for the clarification on everything

ἔρως•2mo ago

this.species <-- this also shouldn't exist, as far as i know no, it works

snxxwyyOP•2mo ago

sorry, what do you mean?

ἔρως•2mo ago

🤔

snxxwyyOP•2mo ago

oh okay why did you think it wouldn't?

ἔρως•2mo ago

because, usually, you use super to access those

snxxwyyOP•2mo ago

like super.species?

ἔρως•2mo ago

yeah

snxxwyyOP•2mo ago

yeah i've seen that as well

ἔρως•2mo ago

but if it works, then it works

snxxwyyOP•2mo ago

do you think it's recommended to use super.species to be safe? or as a more general thing, super.xyz if you're using a value from a parent class?

ἔρως•2mo ago

i don't know why but it doesn't work 🤔

snxxwyyOP•2mo ago

also a quick question regarding this. What would happen if i didn't include species; at the top? The only thing i could think of is that it wouldn't allow you to change it to a private property with # if you wanted.

ἔρως•2mo ago

if you try to access the value before this.species, it wouldn't exist

snxxwyyOP•2mo ago

does it say it's undefined for you when you do that?

ἔρως•2mo ago

yes with super.species

snxxwyyOP•2mo ago

yeah that's the same here did they perhaps change the way it works?

ἔρως•2mo ago

no, but i might have misunderstood it

snxxwyyOP•2mo ago

oh okay so if i tried to access it before i defined it in the constructor it wouldn't exist?

ἔρως•2mo ago

exactly

snxxwyyOP•2mo ago

ah okay i see thank for your help

ἔρως•2mo ago

you're welcome

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