JavaScript Class Static Method, but in function? [duplicate]

Question

As far as I know there are 2 ways to create classes in javascript, with functions or class statements. If in the statement class, you can create static methods using static keywords. Then if it functions, how do you create static methods?

class SomeClass {
  myMethod() {
    console.log("Some");
  }
}

// equivalent to

function SomeClass() {
  this.myMethod = function() {
    console.log("Some");
  }
}

==================================================
==================================================
//Now static method

class SomeClass {
  static myMethod() {
    console.log("Some");
  }
}

// equivalent to

function SomeClass() {
  ???
}

Does this answer your question? Class vs. static method in JavaScript — Object.assign(SomeClass, { myStaticMethod1(...args){ … }, myStaticMethod2(...args){ … } }). — Sebastian Simon
– Sebastian Simon, Commented Jun 27, 2020 at 5:05

FZs · Accepted Answer · 2020-06-27 05:21:07Z

3

Static methods are simply methods put on the function itself. So, it's rather:

class SomeClass {
  static myMethod() {
    console.log("Some");
  }
}

// equivalent to

function SomeClass() {}

SomeClass.myMethod = function(){
  console.log("Some")
}

Also note (although this is off topic to your question), that your first two codes aren't equal.

They behave identically up to a point, but they're different.

classes define methods on their prototype, while your function stuff creates it on a per-instance basis. Thus:

class SomeClass {
  myMethod() {
    console.log("Some");
  }
}

function SomeFn() {
  this.myMethod = function() {
    console.log("Some");
  }
}

const a = new SomeClass
const b = new SomeFn
const a2 = new SomeClass
const b2 = new SomeFn

a.myMethod() //Some
b.myMethod() //Some

console.log(a.myMethod === a2.myMethod) //true
console.log(b.myMethod === b2.myMethod) //false

Therefore, it rather should be:

class SomeClass {
  myMethod() {
    console.log("Some");
  }
}

// equivalent to

function SomeClass() {}

SomeClass.prototype.myMethod = function() {
    console.log("Some");
}

edited Jun 27, 2020 at 5:21

answered Jun 27, 2020 at 5:08

FZs

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2 Comments

Sebastian Simon Over a year ago

… which is already covered by the answers in the proposed duplicate target.

FZs Over a year ago

@user4642212 That's true, but I started writing before you found it. I did a quick search, but found nothing...

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