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JavaScript Instanceof Operator

Description

Sometimes you want to know whether an object was derived from a specific class. To do this one can use the instanceof operator.

Syntax

class Parent {
  constructor(name, parentChild = "Parent") {
    this.parentChild = parentChild
    this.name = name
  }

  speak(line) {
    console.log(`${this.parentChild} ${this.name} says '${line}'`)
  }
}

class Child extends Parent {
  constructor(name) {
    super(name, "Child")
  }
}

let parent = new Parent("Father")
let child = new Child("Gregory")

console.log(parent instanceof Parent) // true
console.log(parent instanceof Child) // false
console.log(child instanceof Parent) // true
console.log(child instanceof Child) // true

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